[wwalexander]

iOS supports using one keyboard for two languages (for me, a USA keyboard with English and Italian). Unfortunately this doesn't exist on macOS yet.

[IIsi50MHz]

Sorta. macOS "Japanese – Romaji" input method supports capslock to switch between English and Japanese (easier than using the standard keycombo).

[wwalexander]

You can configure macOS to switch between languages by pressing the globe key, but it’s a far cry from letting you type in any of your languages without it autocorrecting/red-underlining.