White Americans have gotten along fine throughout our history, with the French, Dutch, Germans, Irish and some Scandinavians here pretty much from day one. Sure there was occasional friction between the Irish and English and later on towards Italians and some Eastern Europeans, but nothing major, and eventually all assimilated to the predominant anglo culture and by ww1 were fighting and dying with each other as Americans on European battlefields. It was a largely successful experiment. It was proof Europeans were all similar enough to do well together once they adopted a similar language and identified as one nationality. I'm not saying that should be the case for Europe, or even Australia and Canada, but in the US it worked well and made white Americans unique among European people. "whites" in the US still generally have 100% European ancestry, and given how Europe is doing these days, are probably far more white than much of the modern European gene pool.

In the US, diversity didnt become a codeword for white hating subversion and demographic warfare until well after ww2.