Can a divided America survive?

The United States is currently the world's oldest democracy.

But America is no more immune from collapse than were some of history's most stable and impressive consensual governments. Fifth-century Athens, Republican Rome, Renaissance Florence and Venice, and many of the elected governments of early 20th-century Western European states eventually destroyed themselves, went bankrupt or were overrun by invaders.

The United States is dividing as rarely before. Half the country, mostly liberal America, is concentrated in 146 of the nation's more than 3,000 counties -- in an area that collectively represents less than 10 percent of the U.S. land mass. The other half, the conservative Red states of the interior of America, is geographically, culturally, economically, politically and socially at odds with Blue-state America, which resides mostly on the two coasts.

The two Americas watch different news. They read very different books, listen to different music and watch different television shows. Increasingly, they now live lives according to two widely different traditions.

Barack Obama was elected president after compiling the most left-wing voting record in the U.S. Senate. His antidote, Donald Trump, was elected largely on the premise that traditional Republicans were hardly conservative.

Red America and Blue America are spiraling into divisions approaching those of 1860, or of the nihilistic hippie/straight divide of 1968.

Currently, some 27 percent of all Californians were not born in the United States. More than 40 million foreign-born immigrants currently reside in the U.S. -- the highest number in the nation's history.

Yet widely unchecked immigration comes at a time when the country has lost confidence in its prior successful adherence to melting-pot assimilation and integration. The ultimate result is a fragmenting of society into tribal cliques that vie for power, careers and influence on the basis of ethnic solidarity rather than shared Americanness.

History is not very kind to multicultural chaos -- as opposed to a multiracial society united by a single national culture. The fates of Rwanda, Iraq and the former Yugoslavia should remind us of our present disastrous trajectory.

Either the United States will return to a shared single language and allegiance to a common and singular culture, or it will eventually descend into clannish violence.

Does the unique American idea of federalism still work, with state rights and laws subordinate to federal law? We fought a Civil War that cost more than 600,000 lives in part to uphold the idea that individual states could not override the federal government.

Yet sanctuary cities declare that they can freely nullify federal immigration law. The California Senate passed a bill earlier this month that would prohibit the state from contracting with any firms that work on the federal government's wall at the border with Mexico.

States such as California vow that they will ignore Washington and work directly with foreign nations to promote their own policies on global warming. Read carefully what some prominent Californians are saying about the federal government: It is not much different from what influential Confederate South Carolinians boasted about in 1860 on the eve of secession.

The national debt has almost doubled over the last eight years and at nearly $20 trillion is unsustainable.

Entitlement spending rose even as new taxes increased. The have-nots claim the haves make far too much money; the haves retort that they pay most of the income taxes while nearly half the country pays nothing.

Most Americans agree that the present levels of borrowing and spending cannot continue. But many believe that the tough medicine to cure the disease of chronic annual deficits and mounting debt is unacceptable.

America's infrastructure and military are vastly underfunded, even though some voters want more subsidies for themselves and apparently others to pay for them.

America's once-preeminent colleges and universities are fatally compromised. Universities charge far too much, resist reform, expect exemption from accountability, and assume their students must take on huge amounts of debt. Yet campuses can't guarantee that their graduates are competently educated or that they will find jobs.

Illiberal attempts to end free speech, to sanction racial and gender segregation, and to attack rather than argue with opponents are disguised by euphemisms such as "safe spaces," "trigger warnings" and various -isms and -ologies.

Behind the guise of campus activism and non-negotiable demands is the reality that too many students simply are unprepared to do their assigned work and seek exemption through protests in lieu of hard studying.

America barely survived the Civil War of 1861-65, the Great Depression of 1929-39, and the rioting and protests of the 1960s. But today's growing divides are additionally supercharged by instant internet and social media communications, 24/7 cable news, partisan media and the denigration of America's past traditions.

All Americans need to take a deep breath, step back and rein in their anger -- and find more ways to connect rather than divide themselves.

They should assume their opponents are not all sinners, and that their supporters are not all saints.

Things are bad now. But our own history suggests that if we are not careful, they can get even worse.