Programming

US-defaultism has a catch: it sometimes accidentally extends to the Commonwealth. You won't run into most of the internationalization quirks if all you're comparing is "British English vs American English".
[Sidebar: I notice this also when English speakers online assume that their audience at least has a vague idea of what Imperial units are, but while that is true of most native English speakers in the northern hemisphere who use feet and miles colloquially, for ESL audiences it's almost always incorrect]

I switched from AZERTY to US QWERTY permanently specifically to avoid all the issues of badly internationalized software. Bad default bindings (e.g. common vim operations like { requiring the use of AltGr), but also things like games not working at all or only partially (e.g. the number row being either unbindable, or key hints naively showing as "&" and "é" instead of "1" and "2"). Surprisingly few devs understand the difference between key codes and characters, and lots of indie games straight up don't even internationalize and require switching layouts (good luck if there is an in-game chat).
After getting into mechanical keyboards, the ANSI US keyboard layout has been useful as well because these are quite common. ISO mechanical keyboards are rarer, and Belgian AZERTY keycaps are borderline nonexistent.

Also in practice I use the qwerty-fr layout which is the US layout with a French layer on AltGr. The kicker? It's better at writing French than the French AZERTY which is missing a lot of letters (Ç, æ, œ, À, ...). AZERTY is a terrible layout but that's a separate discussion.

Of course the Americans should develop properly internationalized software, but I personally know several fellow Belgians who switched to QWERTY for (some of) the reasons outlined above.