USA almost certainly spies on Israel (and everyone else) far deeper than anyone spies on them.
It's hilarious listening to CIA insiders talk about spying.
John Kiriakou [1] will spend 3 hours talking about the CIA's torture program (illegal) and NSA spying on Americans (illegal). In the same conversation, he will insist that the US would never spy on Israel because it is illegal.
Who is this fooling ?
[1] Senior ex-CIA official, whistleblower & internet meme phenomenon.
Who knows who's telling the truth these days. [1] I just assume it's always spy-vs-spy every which way from Sunday.
Since the 1951 Angleton-Harel Secret Pact, there has been an unwritten agreement that CIA and Mossad will not spy on each others countries. Kiriakou (who is a wonk) confirmed as much in recent remarks.
But no one without at least a TS really knows
Quod licet Iovi, non licet bovi
They sure do, but looking at recent events, you can make an educated guess on which country has more influence over the other. Part of it can be attributed to spying and knowing dark? secrets.