is it hard to move to israel from U.S.?

That depends on them.

There are too many factors I don't know that I can't answer this question with certainty. Does she have family there, or does he? Do one or both know Hebrew or even Arabic? Do they have jobs waiting for them? Do they have money saved up? Do they know where they want to live and, would they be fine living anywhere?

A yes to any of these questions would make it easier to make the transition, though normally it is hard to move to any foreign nation that is different enough from your own.

It is quite easy to move from the US to Israel but I am not sure why anyone would want to at the present time. Israel is finding things a bit tough at the moment and the cost of living is high.

Well, there's not much land left at the moment. But don't worry, you never know when Israel invades another country. Keep your hopes high.

Document-wise:

If you're Jewish, it's very easy.

If you're not Jewish, it's very hard.