America's new tribalism can be seen most distinctly in its politics. Each tribe is headed by a rival warlord whose fighting has almost brought the national government in Washington to a halt.

Some inequality is good in terms of giving people the incentives to work hard, invest, invent, innovate. But when so much income goes to the very top, and the middle class and poor don't have enough purchasing power left to buy what the economy is capable of producing, it means we are subject to very anemic recoveries, booms and busts and very high unemployment.

The rich are not the job creators. The job creators are the vast middle class and everyone aspiring to join them, whose money businesses need in order to justify expanding and hiring.

[on what Canadians could learn from Americans in 2013] That inequality of income, wealth and opportunity on the scale we're experiencing it threatens the economy and democracy...We know that resignation can turn to rebellion when the resignation festers for many years, with a great deal of anger below the surface. These sorts of circumstances are ripe for demagogues who seek to build up their own power by exploiting frustrations and resentments, and directing that anger toward scapegoats that have little or nothing to do with the underlying problems.

[on what Americans might learn from the Canadian experience, 2013] That it is possible to have a health care system that works reasonably well and covers almost all the population; possible to control the use of firearms without trampling on individual rights; and possible to craft a system of federalism that provides a significant amount of autonomy to individual provinces, while maintaining an effective national government.