If American haven't intervened, how far would ISIS have expanded by now?

Title. If US didn't step in, how far would have the Islamic State expanded by now? Past Kobane? Past Baghdad and Aleppo? Into Saudi Arabia, Jordan and Israel?

 

Most likely not. Don't you think Iran, Turkey, Saudi Arabia and other nearby states have it in their interests to not be invaded by ISIS? Each of those states alone could take on ISIS. It's not as if ISIS is an unstoppable behemoth that will eventually take over the whole world, although some people seems to think that. It's a bloody terrorist organisation, and they managed to take over areas of two failed states. Oh my, what a feat /sarcasm. They don't stand a chance against any of the nearby states. They just haven't bothered to do much because it doesn't really affect them yet, because americans and westerners might handle it, and because they perhaps like to see iraq and syria weakened.

 

The right question to ask now is where the ISIL will get if America and Europe don't intervene strongly and determinately. If this terroristic organization gets a very strong influence over Libya, one of the most important countries of the area for its strategic position and for its economy, they will have new possibilities of political expansion toward Africa and other Maghreb states.
Thus I think, it is absolutely necessary, in the current situation, to military intervene and restore the control over the territories of the countries affected by ISIL.