It was Israel that bombed the Iraqi nuclear reactor. If it had not, Iraq would have had nuclear weapons making action against Iraq very difficult.
It is Israel that tests US weapons systems in real world combat situations giving a tremendous amount of feedback to improve the weapons systems.
The Tom Cruise movie "Top Gun": It was Israel that stole the MIG fighter jet that enabled our government to understand the operating characteristics so as to train US higher pilots to fight the MIGs.
Israel serves as an "aircraft carrier" for the US where many, many weapons are stored. US troops train with Israelis.
It is Israeli drone which protect NATO troops in Afghanistan including German troops. Israel is the 3rd largest exporter of weapons technology to India after US and Russia.