I know for a while the USAF was operating some Aeritalia G.222 transports, I can't remember the American designation for them, but I heard they'd been liscence built by Chrysler.
They also used BAe Jetstream transports under the C-21 designation.
On the matter of DeHavilland machinery, I belive they still have some Dash 8s in service.
I'd also heard that a few Canadair built Sabres with Orenda engines had found their way into American service as they did have a higher thust to weight ratio than most American built Sabre variants.
But if you want really unusual, I seem to recall reading a magazine article within the past few years about a U.S. Army unit that got set up after the Warsaw Pact was disolved, the U.S had gotten some surplus Hind gunships as some sort of deal with one of the former Warsaw Pact nations and the unit was set up to evaluate the Hind. I'm not sure where the unit is, if its still around or what their Hinds looked like, but it was certainly interesting.