The biggest difference between the current wave of immigration and that of a hundred years ago is that the previous wave eventually stopped, and the fact that it stopped is largely responsible for why it is considered to have been so successful. The long period from 1920-1960 of little to no immigration gave society time to digest all the newcomers. In 1920, the average immigrant was fresh off the boat, didn’t speak much English, had six or eight kids taking up seats in the public schools, cooked weird-smelling food, and may well have harbored a radical political ideology. Those kind of immigrants got natives agitated just like the natives are agitated now. By 1960, the average immigrant was the nice old man with the accent who ran everyone’s favorite pizza joint and voted Republican. Everyone loves that nice old assimilated man.
For the current wave of immigration to work the way the previous one did, it’s going to have to come to an end some time soon. Otherwise, immigrants will never be the nice old man. They’ll always be the guy in the wife-beater hanging around the Home Depot parking lot whistling at your wife and peeing in the bushes. If the U.S. continues to take in a million immigrants a year forever, how can it not dramatically change the country? A lot of immigration proponents think the country needs changing; most people don’t. A lot of immigration proponents also think that immigration policy should be decided based on what is best for the immigrants; again, most people don’t, and rather believe it should be decided based on what is best for the current citizens.
Did the earlier immigration wave change the country for the better? I guess it depends on your point of view. It made the country a lot more Catholic. If you’re Catholic, or agree with the politics of the Catholic Church, that’s great. If you don’t, it’s not so great. It also impeded the economic progress of blacks and delayed the resulting civil rights movement by forcing black Americans to compete with millions of European immigrants for a limited number of jobs. That was not so great either. I’m not saying there weren’t positives, but I believe a fair assessment has to include the negatives as well.