"Thomas Schoene"
No.

http://www.rafcareers.com/thebigpicture/eligibility.cfm

"2. To join the Royal Air Force you must at all times since birth have
been
a citizen of the UK, the Commonwealth or the Republic of Ireland. "

When did this change take place? During WWII I'm sure some Yanks must
have enlisted in the RAF before the U.S. entered the war. 303 RAF Squadron
was manned by Poles. A lot of Americans came up to Canada and joined the
RCAF. The reverse was true during the Vietnam war. Many Canadians enlisted
in the U.S. forces.