You’re fine! I get a flood of asks most days (Gotta dish out that comics know-how!), so it’s a wonder I answer the ones that I do!
Right now, I can’t actually think of any. I am sure there are some SHIELD agents that do, but I don’t know if you would consider them superheroes. Some of the heroes we know from the regular (616) universe might have been reinvented with a military background in the Ultimates universe, but that is a silly place, and we do not go there.
Captain Marvel, of course, has Air Force behind her, which you can read more about here. But as for specifically army, I’m sorry, I’m not much help!