Changing from "English (United States)" to "English" does not work properly without closing the app and opening it again. This doesn't happen if the language change is between different languages that are not dialects of the same root (or from "English" to "English (United States)", it seems to work properly in that direction).

For English in particular, this can be tested by looking at a Quiz's grades. In standard English it uses "Marks", whilst in american English it uses "Points".