The US Navy “allowed” their proximity fuses to be used by British coastal AAA. By that time, it was mostly the V1 that was the target.
(The USN didn’t want it reversed-engineered, so it was used only over water until late in the war, maybe the Battle of the Bulge)
I thought the first use of USN proximity fuzing was at Hurtgen Forest. And yes, the USN was extremely careful with that secret. It was a war winner.