Israel is well aware of the fact that the U.S. has its issues and we currently have our hands tied, and it knows that the survival of their people is mainly dependent on themselves at the moment. Being surrounded by people who are bent on their destruction, I can see why these drill are in place. It is always better to be prepared than to sit back and live in denial like a lot of the people right here in the U.S.
If we did these drills in America can you imagine what the 'far left' would have to say about scare tactics by our 'far right'? It would be a mess.
Israel knows they are on their own to some degree. At least politically.