Us and Israel have too much to defend in these times to drop one another. They're our strongest ally and as far as I'm concerned they're really the only other country that matters in this world.
Name one thing that Israel has done for the United States.
I... agree with Snowstalker. What does Israel do for us to merit the support they receive? Obviously they deserve their country, I guess, but that's their problem.
I also sort of agree with Adam Griffin in that I almost feel that the two sides should be left to run rampant. Let the Israelis take over the West Bank and evict the Palestinians, or let the Arabs conquer Israel and let all the Israelis come to the United States.
The latter is probable enough that it should compel some anti-Zionists to reconsider their position. Not only that, but barring an establishment of a Jewish state it's likely that would have happened, as well.
Because seriously, what would you do with the Israelis if Israel was to cease to exist, short of, well, killing them?
While I've come to think that American financial aid to Israel is more trouble than it's worth, especially with the coming oil boom of Tamar and Leviathan (and don't think this is unrelated to the increased efforts to destroy Israel - lot of people want those oil fields), there's another factor.
Israel has the best tech sector in the world. The US' staunch support for Israel puts them in the position of being able to get first grab at new technologies, many with military application. They can also negotiate exclusives that keep that tech out of the hands of rivals.
A full financial and diplomatic cut-off for Israel would give Israel no choice but to open that tech to the highest bidder. So a friendly relationship between the two is definitely to the US' benefit. Nor is there any legitimate reason for the US to cut off diplomatic support for Israel.