"Polarized" may well be the most overused adjective in American politics today. Employed to lament our deep national divisions, it's usually followed by nostalgic pining for a gauzy past when Americans set aside their differences for the common good.

The thoughtful response the next time someone drops the "p" word into a conversation would be: "It has ever been thus." According to "American Nations," a provocative 2011 book that reinterprets U.S. history in ways both reassuring and unsettling, it's the norm, not the exception, for our country to fall far short when it comes to putting the united in United States.

Deep divisions were present among the colonies and regions that came together to fight the British and forge a new nation over 200 years ago. Deep divisions remain, as anyone knows from studying election-night maps that sort America into "red" states and "blue" states. But "American Nations" author Colin Woodard makes the compelling, if not entirely new, argument that the fault lines are more complex -- and more interesting -- than the conventional wisdom about north-south and urban-rural divides.

Woodard, a Maine author and journalist, builds on previous work about North American folkways to argue that we have multiple regional cultures in North America -- areas whose distinct identities, values and institutions make them virtual nations within our union. And he says these internal nations have been engaged for more than two centuries in a kind of Cold War struggle (with a notable outbreak of actual war in the 1860s), vying for dominance of the federal government.

It takes a leap of imagination to accept the idea that these regional "nations" were primarily shaped by early, mostly Western European settlers and that despite immigration and modern technology, subsequent generations have acclimated to the cultures that were originally deposited. How these national identities interact with race and gender are also unanswered questions. Yet readers will likely find that they intuitively recognize that these nations exist on some level.

Woodard backs up his argument with voting data that show the nations' cohesiveness, even across state lines. But the dominant characteristics he describes for each nation are familiar to anyone who's traveled even a little around the United States. Once you read the book, you can't stop seeing these national identities and rivalries rearing up in everything from politics (Nebraskan Chuck Hagel's confirmation struggles with Southern and Western senators from his own political party) to pop culture. "Here Comes Honey Boo Boo" is a TV window onto a Southern society that, to the average Minnesotan, may be more "foreign" than are half a dozen European countries.

Having distinct nations within our borders doesn't make America unique -- think Turkey with its Kurds, Spain with its Basques, or Great Britain with its Scots and Welsh. Where America differs is that we rarely acknowledge our separate cultures. Our American nations deserve a more prominent role in our collective consciousness so we can quit mourning a mythic unity and better understand the forces that have long divided us and will continue to divide us over everything from the federal budget to foreign affairs to health care.

"We have all these arguments about what are American ideals or the American identity," Woodard said in a recent interview. "Everybody tries to go back to the founding fathers for the answers, but that's far too late in the story. The real answers -- and they're multiple, competing answers -- go back to the foundation of regional cultures 50, a hundred, or 150 years before 1776."

So what are these nations? Woodard argues that there are 11, but four have long dominated the continent:

1. YANKEEDOM
This is Minnesota's nation, thanks to influential early settlers from New England. Yankeedom stretches from the northeast to the Great Lakes states and is rooted in the utopian communities founded by Puritans. Its defining characteristics include a respect for intellectual achievement and a deep faith in public institutions' ability to perfect society, which is why other nations view it as a busybody that likes to mind other peoples' business. In Yankeedom, individuals are expected to sacrifice for the common good, which meant one of early settlers' first priorities was to tax themselves to build schools and local government. (Seen through the Yankeedom lens, is Minnesota's newly DFL-controlled Legislature simply its dominant nation reasserting its prominence? Discuss.)

2. MIDLANDS
Often dubbed the "Heartland," it includes most of Iowa, much of Nebraska and Missouri, as well big chunks of Pennsylvania., Illinois, Ohio and Indiana. The Midlands culture is rooted in Quaker communities founded by those who fled Old World tyranny and came to live their lives in peace. Moderation, pluralism and pragmatism are the Midlands' defining characteristics, along with a definite pacifist streak. A live-and-let-live philosophy creates skepticism about both big government and big business. Like Yankees (but without their scolding tone), Midlanders believe society should be organized to address common needs.

3. DEEP SOUTH
Stretching across the southeast United States from east Texas to southern North Carolina, the Deep South is a "stratified, oligarchal society founded by English slaveholders from Barbados," Woodard writes, and the "polar opposite" of Yankeedom. A society engineered at its founding to serve the wealthy few has preserved an acceptance of inequality as the natural course of human society and a skepticism about the notion of common good. One modern-day expression: a hostility to environmental regulation. Long-held notions of honor also lead to a readiness to resort to force to settle disputes.

4. GREATER APPALACHIA (aka the Borderlands)
A mostly poor but proud backwoods Southern culture, the Borderlands stretch from western Virginia to central Texas. Settlers shaping this culture came from Britain's rebellious northern border areas and Ireland. Defining characteristics include a warrior ethic, a suspicion of authority, and a gut-level resentment of any limitations on individual liberty. Religion here also emphasizes fervent individual faith, elevating personal salvation over good works -- a spiritual focus shared with the Deep South.

Other nations include Virginia-centered Tidewater, with its more genteel and enlightened version of Deep South society; the libertarian Far West, and the Left Coast, a socially and technologically adventurous Yankeedom colony from central California through the Pacific Northwest. New Netherland is a diverse commercial enclave encompassing the Dutch-settled New York City area. El Norte is the heavily Hispanic culture along the southwest border. Citizens of New France, a culture that includes the Cajuns and Quebec, may well be the most socially liberal in North America. First Nations, based in far northern Canada, is an increasingly influential culture shaped by Native Americans.

Keep in mind that these nations are simply the dominant culture in each region. Not everyone in Yankeedom is a Yankee. That, along with the tendency of like-minded people to cluster together in neighborhoods or communities, explains why Tea Party firebrand and Republican Congresswoman Michele Bachmann hails from Minnesota. At least, that was Woodard's take on Bachmann's Sixth District victory streak.

The nations outlined by Woodard aren't political-science mainstream. Nor are they the sole explanation for our differences. But seeing America, from the beginning, as a tense alliance among very different, sometimes antagonistic, peoples does help us grasp why we're divided.

Self-awareness of one's own "national" tendencies, and of how others view one's region, have practical political uses. Such insights also answer a question that flummoxes blue states: why do red states so often oppose social programs, such as health care reform, that would benefit their poorer populations?

National differences help answer the riddle. Opposition to the Affordable Care Act, most intense in Greater Appalachia and the Deep South, wasn't just about cynical politics or a lack of information, as blue staters often believe. It also had roots in deeply held beliefs about individual liberty and long-standing fears of Yankee do-gooders telling others how to run their lives. (The Affordable Care Act is heavily influenced by Massachusetts' health reform.)

Knowing that ahead of time might not have changed the health reform law, but it should have prepared its advocates for its fiery reception. Future policy could be marketed or engineered in ways that minimize regional fault lines. It's naive to think support will be based only on an "I'll-benefit-from-this"calculation.

One of the most common and justified criticisms of Woodard's book is that it doesn't go far enough applying the nations paradigm to current events or explaining how differences could be bridged -- if that's possible. In fact, Woodard raises a breakup of the country as a remote but not-to-be-dismissed possibility.

But Woodard's book is grounds for optimism. That we've stuck together for so long despite vast differences and previous secession threats (not just from the South) is remarkable -- especially now that we see how precarious the European Union is. What may make America truly exceptional is that our nations chose to weave themselves together relatively early in their histories. History shows that retrofitting unity onto nations with identities calcified for centuries doesn't work over the long haul.

The American nations also have a long history of forging a shifting array of alliances to achieve federal domination, which in turn acts as a moderating force on other nations' extreme tendencies. Republicans have leveraged similarities between the Deep South, Greater Appalachia and the Far West and have capitalized on Midlanders' big-government skepticism to build presidential election-winning coalitions in the past. With Democrats forging a strong Yankeedom-Midlands-Left Coast-New Netherland coalition in the 2012 election, while making inroads into Tidewater, Republicans need to find new allies beyond their Deep South-Far West-Greater Appalachian base.

El Norte nation voters are a likely candidate, as Woodard wrote recently in a Star Tribune commentary. That, however, will mean an overhaul of the party's anti-immigration plank -- a task that already appears to be underway. Moderation on social issues and a shift away from tax policy primarily benefiting the rich might also increase the GOP's appeal to Midlanders. The takeaway from Woodard's book isn't that Americans are permanently divided, it's that common ground is possible. It's just a much smaller patch of real estate than we'd like to think.

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Jill Burcum is a Star Tribune editorial writer.