I'm pretty sure I wouldn't be butterflied away - I'm Irish on my dad's side, and Afrikaner on my mom's side. And the state I live in - New Jersey - is mostly Irish and Italian, with most of the Germans being of the Jewish variety. New Jersey will probably see very few changes in an America with less German-American assimilation - at least, much fewer than in the Midwest.
To slow German-American integration, keep America out of WWI. That war sparked a tidal wave of anti-German fervor, with the German language being removed from schools and foods like hamburgers and frankfurters being renamed Salisbury steak and hot dogs. Not only would American neutrality in WWI prevent this from happening, it would help Germany last longer in the war, perhaps allowing it to either win the war outright or end it with better terms. With a reasonably powerful Germany in the 1920s, you'd see a swell of pride among German-Americans, stalling their integration even further. By 2000, although the Germans have most definitely been integrated into American society, their culture is far more prominent than it is in OTL, and Midwestern dialects have been heavily influenced by the German language.