Assimilation of the Roman variety (i.e., the main language isn't forced on anyone, but all the popular media and good-paying jobs require it) go brrrrrrrrr.
Economic penetration and entwinement with Anglo empire has sociocultural ramifications (homogenization of social and economic structures to resemble Yankland).
Similar process shrunk a lotta the native languages in the east/north of the USSR, despite state efforts to prevent that.
Class society, capitalism, empire all lead to such homogenization, historically with a large state or market comes homogeneity.
Given enough time I imagine the global north nations would fully anglofy, with the english language turning into a language family (similar to latin turning into the romance languages)