The U.S. has always:
1) responded poorly to successive waves of "others" once the population grew large enough to be something they competed for jobs with,
2) assumed assimilation and when ethnic or religious communities formed and would not be assimilated, they were (are) persecuted legally and socially,
3) let's not even go into how the more you bring with you (wealth, genius, patents, resources) the more welcome you are.