I think both can be true: that we have a Zionist problem and an Iran problem... If things go well, pretty soon we will just have a zionist problem. The fewer problems you have, the easier the remaining problems are to solve.
There's probably going to be some negative consequences for the US; but I don't think there's going to be a prolonged war- and there will be some positive effects that come as well. I wouldn't call it a huge blessing; but there are benefits to an Iran that isn't driven by an ideology that is inherently hostile toward the US.