They and Jordan are the only REAL friends America (as opposed to those assholes in DC ) has over there, and if Israel goes Jordan goes because the fanatics hate Abdullah and have always hated his family. Their crime was trying to improve the lot of everyone by working together rather than harming everyone through constant warfare, that sin makes them outcasts in the Muslim world.
And yes, when Israel goes down it will be in flames, and it will probably take most of the rest of the world along for the ride.
If the Jews start slinging Nukes they will for sure take Syria, Iran, and Pakistan, India will probably jump Pakistan from behind because they hate each other and both have Nukes, Russia is allied with all the arab targets so will fire on Israel, So we will fire up Russia and probably N Korea just because (as BO says no crisis should be wasted) France will also attack Israel, if their missiles work, (never established, doubtful), China would probably hit targets of opportunity and try to be the one to pick up the pieces, While they have a space program they only have a relatively small arsenal and less than 2 dozen launchers so their best bet would be to try to be the last man standing while the rest of the developed world destroys itself.