Germans are the biggest ethnic group in the US already so this is already the case. Also according to Wikipedia, they're the largest ethnic group in Pennsylvania one of the 13 colonies so both parts of your challenge get satisfied.
I'm doubtful on it being a clone of English cooking. What is more likely is an increased influence of the south/east European immigrants.(This comes from the fact that they'll fill the void left by removing southern culture plus without southern labor to come up north, more immigrants come in)...
What's the link to that thread? It sounds interesting to me. However I do have one quibble with the idea you propose. Freeing the slaves won't magically make them disappear. What would be more realistic would be a fusion of east Indian influences with black american influences. Soul food with...
No post 1980 backlash/slowdown in liberalization of sexual morals. What I mean is to somehow keep the 60s and 70s cultural revolutions going on into the 1980s. I think the most likely path for that is to somehow avoid both AIDS and the oil shocks/stagflation of the 1970s.
Interracial marriages have kept on increasing every year since 1967(there was a supreme court case in 1967 which I forget the name of which banned restrictions on interracial marriages) so in a world with early civil rights expect a significantly larger mixed race population than in the real...
I suppose you could either have phone related technology like cellphones get developed faster to speed up the development of mobile phones so they get cheap faster. Either that or wait a few decades to get the same result.
Of course Esperanto would have become the Soviet union's official language. Remember the tagline they used when they introduced it? "A new language for new soviet man!"( yet they ignored the fact that esperanto was thought up in the late 19th century and tried presenting it as a soviet creation...