Earlier immigrants certainly strove to assimilate (in terms of language, work ethic); today the remnants of the WASP culture are expected to be conversant in the cultures around the globe that send their Least Valuable Players here to this country...
Least valuable is right!
My favorite example of a multicultural empire is the Austrian empire.
They used Latin as their language of gov’t administraion until 1784, when the emperor Joseph II, who was an “enlightened despot” like Frederick the Great, replaced Latin with German, because he thought the Germans were the most “advanced” ethnic group in the empire, and he wanted a modern, centralized state.
Well, the result of this was to make everyone in the empire more conscious of their ethnicity, whereas before, it wasn’t such a big deal. Eventually, ethnic conflicts were to bring down the empire.
The Hungarian part of the empire kept Latin until 1846 for their internal Hungarian governmental affairs, then switched to Hungarian.
That was even worse than German, because Hungarian, a non-Indo-European language, is very hard to learn, and Hungary had a lot of ethnic minorities who were bullied by the Hungarians.
The empire broke up after WW1, and the old central European parts of the empire became the killing grounds of WW2.