The person you responded to explains that the most common ancestry in the US is German, but English is the dominant language.
You seem to be making the point that the most common ancestry in England is from England, but the Germanic language of English is dominant, rather than the Celtic one it replaced.
It's the same phenomenon, not a correction. That languages spread even when genes don't.
>The most common ancestry in the US is German, not English, but English is still the dominant language. Language isn't DNA.
Their specific point is that "language isn't DNA". To support that argument they note that Continental German immigrants to America now speak English.
My specific point is that English originates not only within the language family of German speaking peoples, but that it originated with the DNA pools that comprise Northern Germany.
Therefore, I don't see how "the Germans are speaking English" makes the point that language isn't DNA.
I'm not saying that it is, at all. Its very obviously not. But the example being argued didn't make that point.
Your objection is that English is a Germanic language. That's interesting, but irrelevant here. German and English are two different languages that are mutually unintelligible, and the fact that immigrants went from speaking one to speaking the other within a few generations illustrates my point that language does not have to (and often doesn't) follow genetics.
It's not only German immigrants to the US who now speak English. Pretty much all immigrants to the US speak English after 1-2 generations, regardless of what language they originally spoke.
Because German isn't English. Speaking one doesn't let you understand the other in conversation, not even a little bit. They're not like e.g. Spanish and Portuguese.
The fact that English is Germanic is a historical fact about where it came from, what it evolved from a millennium ago. But only a small percentage of Germanic influence remains in modern-day English vocabulary. It doesn't have anything to do with Germans in the US learning English.
But as you say, the relationship between English and German doesn't have anything to do with what we're discussing. English and German are two different languages. Immigrants who spoke German gave birth to children who learned English, and after a few generations, their descendants didn't speak German any more. And that didn't just happen with German immigrants. It happened with every non-English-speaking immigrant group.