system
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human
ELI5: Can someone explain the US's love affair with Israel?

It seems as though the US is in pretty much constant support of Israel and has been for a long time. Why?
gpt
It wasn't always. Back in the '50s the US was generally less supportive than western European democracies like the UK and France. The initial wave of support came from Cold War politics. Whenever the Soviets gained a client the US immediately sought to gain clients to counter balance and if possible to pry the Soviet client back out of the Soviet sphere. So when nations in the Middle East started to buy equipment from the USSR we tried to sell to them as well (Iraq and Egypt) and to make alliances in the area. Israel as a western style parliamentary democracy with a large western population was a natural fit as an ally.

Once the basic relationship was established several other factors have continued it.

First - The continued need for allies in the area. And while there are a number of downsides to siding with Israel (like generally pissing off everyone else in the region), there are good reasons to stay with them. Not least is to prove to other allies across the world that we'll stick with them. So we stick with them to show to countries like Japan and South Korea that we are the type that will stick with them even if China or Russia starts something with them. And Israel has generally been a pretty good ally for the US.

Second - There is a huge Jewish population in the US. In general they support Israel and lobby hard for it. This is even when they disagree with some specific Israeli policies. The idea of maintaining a specifically Jewish nation and homeland is viewed as something that would help should another Holocaust or other lesser pogrom happen again. Israel would in such a case act as both a refuge and someone who could act in international forums. So even when they disagree with Israeli policies, the concept and fact of Israel is enough to maintain their support.

Third - The Evangelical Christians also strongly support Israel. This is generally for doctrinal reasons, mostly to do with the predicted second coming. Millennial prophesies (as they interpret them) require an Israeli state. And this also goes for groups that aren't in the normal Evangelical fold like Mormons. It also influences other non-millennial groups who see their other Christian neighbors supporting Israel and join in... without quite knowing why. This support is also largely independent of any specific Israeli policy.

Fourth - There isn't a large Palastinian, Arab, or Muslim minority in the US. So when the other two groups lobby or otherwise pressure the government to support Israel there isn't much of another side to oppose it. So one side provides funding and votes to the politicians and the other doesn't. And until politicians start losing their jobs for being pro-Israeli they aren't likely to change their tune.