That’s a (not so big) « issue » since it’s a written convention which comes from clocks layout. Even while using the same physical layout, lots of countries count time from 00:00 to 23:59 (without notion of AM/PM).

In France we always use 24h format when writing and usually when speaking. But some people uses the same conventions as US, only when speaking by saying « 3 heures de l’après midi » which stands for « 3 hours in the afternoon ». It tends to disappear however for « 15 heures ». Exceptions are we likely never say 00:00 or 12:00 but « Minuit » and « midi ».

Some people are thrown off when the time goes 10AM, 11AM, 12PM, 1PM. The "12" is used more like a 0. So 0 hours and 30 minutes post meridian is 12:30PM.