Americans are just very scared of Mossad. Tons of money goes into Holywood to make them appear invincible to the world. Fun fact, they aren't.
Intelligence agencies have great capabilities no doubt they get billions of $$$ and have utter immunity to do whatever they want in the name of national security. Why is only Mossad scary? I'd be more scared of the CIA and KGB than of Mossad.
US has never been in existential threat like Israel has been, if it were I wouldn't want to stand in their way.