U.S. has used Harriers...
Just to bring it up, the U.S. has used Harriers as an important weapons platform for the Marine Corps, being as they can take off and land on 'gator freighters' and helo-carriers.
So yeah, lots of cooperation between US'ian and British armed forces.
[how about you guys design/build another major paradigm shift like the Harrier? then we'll buy YOUR planes!]