The melting pot in America requires assimilation
The subject has actually been around since 1965, when Lyndon B. Johnson signed the Immigration and Nationality Act of 1965. The Act made major changes to immigration in the United States, allowing a more diverse population. No longer did we give preference to Northern and Western Europeans. Kennedy was gone; Johnson, one of the most partisan presidents, took the opportunity and went with it.
Since at least Lyndon Johnson, the contemporary inner workings of the Democrat Party are, by any measure, treasonous.
You could say that we stopped searching for engineers and doctors, among others, who could make significant contributions, and instead began looking for future needy Democrats. These Dems would be coerced into continually voting for Democrats lest they lose their handouts.
Since that legislation passed, our population has nearly doubled. That is not the entire problem. The main issue is the new immigrants' origins, culture, and identity. These factors can lead to challenges in integration and social cohesion because vastly different cultural practices and values clash with established norms. In our case, the established norms are Western values.
The melting pot in America requires assimilation. Muslims in general do not assimilate; they dominate. We don't want cultures that demand the cessation of church bells on Sunday morning but require a loudspeaker call to prayer five times a day. We don't want cultures in America that promote segregation or the establishment of separate towns or cities.
If you respect different cultures but would rather not live with a tribe from Papua New Guinea, the Left will label you a racist. The Left ignores this issue, even when it hits them in the head, rapes their women, or murders their children.