This is an excuse that Jewish in America and Evangelicals use to rationalize broader support from Americans. It is almost as weak as the 2000 year old land claim arguments from some Jewish Nationalists, and weaker than the doomsday prophecies that Evangelicals feel obligated to accelerate at the expense of everyone else so they can ride away on a cloud with Jesus while the planet descends into chaos.
The US has bases in almost every surrounding country of Israel, and literally invaded all the countries that border Iran. It can lob missiles and strike at nuclear facilities in Iran if it wanted to from anywhere. It has the rest of NATO on the European subcontinent to keep Russia in check.
The US can easily tell Israel to pound sand and make good on the supposed idea of aligning with Russia. Nothing of value would be lost.
If it sounds absurd to imagine the fiction where Peru is paying for Israel's defense budget, then it is absurd for the US to be involved too.
Probably not. The US supported Israel to keep Iran/Russia in check in the region and frighten the rest. If the US is pulling support, it's probably going to rely on Iran (the legitimate heir?) to run the place. They'll have no incentive to keep propping Israel.
Imo, that's why Netanyahu tried to spark a war with Iran. They went on to make several alliances with Arab countries, in a bid to create a military alliance against Iran. He was wrong, however, in that Arab countries (surprise, Saudia Arabia) was more interested in making peace with Iran than starting an all out war.
For that, Netanyahu tried to spark a conflict and he had the right ammo for this (he knew the guys in Gaza will retaliate). At surface, it looks like Netanyahu hates the Gaza guys (Hamas) and they hate him. In reality, their existence depends on this conflict.
It seems, however, that everyone is willing to move on. There will be peace in the future and also higher oil prices :)