The US has gone through periods of isolationism and being anti-immigrant. Thats nothing new. I think the last time was the 1920s. There are interesting ideas that it has to do with American over-involvement in world affairs and reaching a certain threshold for immigrants as part of the US population.
The influx of Irish, Germans and Southern Italians in the 19th and early 20th centuries lead to a backlash and the passing of restrictive immigration quotas in 1924. This lasted until it was repealed by the Immigration and nationality Act in 1965. That's 40 years of extremely restricted legal immigration.
Interestingly many economists attribute at least some of the post-war prosperity of the 50s and 60s to these limitations.
The open borders policies of the Democrats are not sustainable. No nation can survive without some border security. Another backlash is inevitable.
*MySmiley*
"Bustin' makes me feel good!"
Ghostbusters, by Ray Parker Jr.