Dealing with this plague "country by country" is in effect similar to what we would have done in World War 2 if we had tried to free German occupied nations country by country without ever bombing Berlin.Germany and Japan were countries. Islam isn’t. It’s spread across a wide portion of the globe. The problem with that is, even should we have complete victory somewhere, it’s tentacles will still be active elsewhere. That’s a different scenario than going head to head with an expansionist country.
You’re right in that we’ve lost the will for total victory. But even worse, we’ve lost the knowledge that the West and Islam are incompatible. And that only a total commitment to destruction of its host regions of power (Mecca, etc) should they attack would suffice. We don’t think that way and the will isn’t there in those who we’ve put in power.
Dealing with this plague "country by country" is in effect similar to what we would have done in World War 2 if we had tried to free German occupied nations country by country without ever bombing Berlin.