Yes we would gain a lot of territory if we took out Syria, Iran and Iraq but over all we would be losing territory African territory such as Sudan is about to drop into an even more extremist Islam hands, the Philippines is a target and other far east countries. But those three countries are presently strong points and it would be a good thing to take them out.
Sudan is NOT about to drop into an even more extremist Islam hands It already did over 20 years ago!
What is going on in the Philippines has been going on as far as my Pilipino friend's grand parents remember. Maybe a change in "the cause and terrorist affiliations", that's it.
We obviously can't occupy 200 countries at once. The way to deal with the WoT is to deal strongly with the closest danger and steadily erode the terrorists' supportive systems and governments. Can you say the Bush Doctrine?