Joseph, If the Americans and English are two peoples separated by a common language how much more so Yiddish speakers. When a Galitzianer says ‘Elokeini” a Litzvak thinks that he is saying “My Gd”. For that matter, Yiddish has many loan words from whatever is the local language. In fact, Ruchama Shain commented in “All for the Boss” that when she returned to NY form mir her relatives did not understand her son’s Polish Yiddish as they spoke American Yiddish.
Ben Levi, Ponevich has many Chassidic talmidim and even waives the no beards rule for Chassidic bachurim (Litvaks consider it haughty for a bachur to have a beard). Rav Schach was very much opposed to ethnic discrimination.
JF, there are many mixed minyanim. In fact, my weekday Shacharit minyan goes according whatever the Shatz davens. If there is a pinch hitter in the middle it switches.