Another important example seems to be the cavity magnetron in WWII. Developed in the UK, it provided about a thousand times more power than the klystrons the US was using at the time and let the Allies maintain a lead in radar technology: probably an important component of the Allied victory, though under appreciated by the public at large. UK designed, mass-produced in the US. The “Tizard Mission” that this was a part of sounds pretty fascinating and I’ve always told myself I’d pick up a book on it someday.