I think they are essentially claiming that "Americanism" has lower standards than the ethnicities that moved to America as refugees. So the people who were refugees, like all the jewish physicists in the Manhattan project came from culture that valued higher education and socially liberal society and all those good things, while American culture doesn't, so getting them "americanized" makes them value higher education etc less.

Which would be incorrect, as Manhattan ALSO has a hyper conservative Orthodox jewish population which did not assimilate largely and basically caused measles outbreaks because they are vaccine "hesitant"