If the US backs out the hard liners gain even more control, ally with china, and begin their final solution to the palestinian problem. Israelis would go north korea before a one state solution.
Which is exactly why they'll feel like a cornered animal and become even more violent. Israel has a competent defense industry, they do not need foreign aid to run their military. What they need is foreign aid in order to semi humanely run their military at a price theyre happy with. Foreign aid pulling out wont end their military, itll just make it less humane and even more reckless.
The thing is, Israel needs to worry about its own defense too. Currently there are several semi-hostile neighbors that the US basically pays off, plus the US pays for very expensive defense systems in Israel. Last invasion was long ago, Yom Kippur War, where the US was withholding aid until Israel started losing and suddenly it became an airlift scramble. But more recently there were the two Iran wars where thousands of drones and missiles had to be shot down.
Israel has nuclear weapons. If all their foreign backers pull out they would use them in an invasion scenario, so I dont think they need to worry to much about hot war with a legitimate government.