Mitchell Plitnick diagnoses it:

Sometimes, Americans follow Israel’s lead. Sometimes we don’t. It’s part of a dynamic many Israeli friends of mine, across the political spectrum, have expressed exasperation about: Americans being more “Israeli” than Israelis. It’s a grossly fetishistic exercise, one that says more about projecting American religious-political desires onto Israelis, than it does, necessarily, about what Israelis might want and think, by themselves.

It is, from an outsider's perspective, a strange phenomenon. It took a while in America for me to grasp why the media and political world was fixated on a tiny country with almost 8 million people. No conspiracy - just a fervent ethnic and religious solidarity that sometimes borders on self-parody. The US Congress is integral to this lop-sided near-fusion of the US and an increasingly problematic ally in a fast-changing region. Plitnick notes the following from the NYT: