Regarding migrations, one clarification.<p>American society so far has demonstrated a tendency to alternate between mass migrations coming in from abroad, and mass <i>internal</i> migrations.<p>The last great internal migration was the 1940’s to 1970’s as cars and highways became widespread.<p>The period of mass migration from abroad coming in happens in the mid 70’s with significant events being Vietnamese refugees in 1975 and Iranian refugees in 1979. The end of the Cold War meant the stopping of US support to many anti-communist dictators which also increased these numbers. I believe though it was a change in the immigration law in 1965 that made this possible, which reversed the quotas put in place in the mid 1920’s and established family unification as a priority.<p>With that all being said though, it seems that mass migration from abroad has become more controlversial in the US, and perhaps we are entering the next great age of internal migrations.