Short answer, it's "complicated" in that there are always multiple things going on at once, but... yes. And the ways it's "complicated" are weirder than you might think. Like that Germans were actually one of the least "assimilating" significant non-English European populations here in the 19th century. Actual histories often don't match our assumptions based on current ideologies.
Fighting Everything German in Texas, 1917–1919
https://www.jstor.org/stable/24449071
"…World War I not only intensified fears that the "melting pot" was failing, but also broadened this concern to include German Americans as a suspect ethnic group. Before the war, German Americans were one of the most respected immigrant groups in America, having achieved success in many spheres. Brewery magnate Adolf Busch, intellectual and U.S. Senator Carl Schulz, and financier John D. Rockefeller were among the German Americans who had risen to prominence in the United States. Significantly, German Americans acquired their favorable reputation despite being the ethnic
group most resistant to assimilation…"
"…Furthermore, Texans’ historic distrust of German Texans helped inspire anti-German activities. During the antebellum period, slaveholders had viewed German Texans with suspicion, especially after an 1854 convention of German Texans adopted an anti-slavery resolution. In fact, only a minority of German Texans supported this resolution, but most Texans did not understand that subtlety. They were preoccupied with German Texans’ common culture which prevented them from discerning political, religious, and social differences among Germans…"
"…Claiming that German Texans’ ethnicity was equivalent to disloyalty, many council of defense members in Texas were determined to purge all traces of German culture from their state…"
(DOI: 10.1111/j.1540-6563.1994.tb00925.x for your sci-hub needs...)
But my main point is that these are very different situations -- national projects in Europe unifying/homogenizing various long-existed local geographically-specific cultures (I'm not sure 'assimilation' is even the right word here). Vs America, where various European populations came, only in the last few hundred years, displaced local geographically-specific cultures, and then competed with each other for political power or cultural hegemony as they expanded to take land the previous occupants were displaced from, also sometimes forming communities together (in which they were all newcomers to the land). Just two very different situations; although i tried to say there were some commonalities in the way cultures are homogenized/unified, I am sympathetic to the idea that "why are you even looking for commonalities these are such different situations".
I think we often over-simplify the diversity of historical paths with this stuff, assuming that the way we now look at "culture" or "nationality" or "race" has always been the way people did, and/or was inevitable. But these things were built, in the not too recent past, and didn't work the same way they work now even in recent history, and worked differently in different places.