Comment 3 for bug 1801498

In the Calamares welcome screen, languages are sorted in the list by their ISO language name (e.g. Russian, Korean, Greek, etc.) but their native language name (e.g. русский, 한국어, ελληνικά, etc.) is displayed. Languages with different localized variants (look at Spanish/español) are grouped together. There is one exception to this: American English is always at the top. It seems there is a bit of reluctance in doing so, but it is certainly intentional:
https://github.com/calamares/calamares/commit/59537d86d65ffc190cd2f74587b2893161065c19
That said, it's certainly not random. The other Englishes are where they belong. It's just American English that's weird. Strange, but not terrible. If you don't need American English, it's not even strange.