One should go through the conflicts of 1920-1930 and see if there were air-to-air combats in any of them. A quite thorough list of aces and air victory claims of all conflicts can be found here:
http://aces.safarikovi.org/
Looking the list the nearest thing to US air victory claims of 1920īs seem to be those claimed by Marion Hughes Aten in RAF service in 1919 against Russian Red Army air force. Details:
http://www.americanfighteraces.org/ww1aces_russian.html