I live 2 towns east along the Ohio River from Covington, in Fort Thomas. I'm working on a book of Kentucky baseball history and while this area was a hotbed of semi-pro teams I haven't come across the "U.S.A." team yet. One possibility is that Fort Thomas was an infantry outpost and for years fielded the best baseball team in the Army. I am familiar with the
1890's version of the team which was called the Cochran's after their commanding officer, but these guys look like they are from a little later maybe 1905-1920.
"U.S.A." could stand for "US Army" and if it was taken in Covington that would make sense since that is just 3 miles from the fort. I'll let you know if I run across any other Covington area team that would fit. Good luck and neat photograph!