> Canada is nothing but diverse, in a very similar way to the US and somehow it’s never used an excuse.

Less than 20% of Canada is a "visible minority." In the U.S., it's almost 40%. Toronto recently became a majority minority city. Washington, D.C. became a majority minority city sometime in the 1950s. In Chicago, it was sometime in the 1980s. Canada has no majority-minority provinces. Ontario is still 67% European (roughly on par with Connecticut). Our two largest states, California and Texas, are both majority-minority states.

Recency matters too. Much of Canada's diversity is very recent. American politics has in contrast been shaped by these conflicts for decades (really, from inception--we fought a whole civil war over race!).