What tanks, used by the US Army, are being made in a foreign country? To note, the only actual tanks in use by the military are the M1 Abrams and it's derivatives, and possibly the M551 Sheridan (unless the 82nd Airborne has finally turned those into the machine gun targets they richly deserve to be).

As for M16 ammo... I think the Israelis have a factory that makes it, but the vast majority of the M16 ammo (.223) comes from a US Army owned arsenal in the US.