The green card clearly is not that imminent if OP is talking about a gap year. And whether or not they can leave entirely depends on the type of visa they are on now. If they have existing H or L visas or already have advance parole on another type of adjustment application it is not a problem to leave. Anyway it’s a moot point if going back to Israel means OP has to join the army, that’s what makes it a non-starter. But by the same token being the derivative of most of those visas means OP is not going to be able work in the US on a gap year. So a plan B for taking a gap year means finding another way to strengthen the application.