I believe it is careless to wear an 101st airborne shirt as a merc there,
The Russians weren’t going after the foreign mercs, they were targeting a meeting of Ukrainian commanders at the 56th Motor Brigade HQ.
I agree it’s careless to wear American gear there, but these mercs are just like that. They like to look cool. It’s certainly a tipoff the guy is really a merc not currently serving (if he ever did) and is not a “gray suitcase”.