You say we're in afghanistan because islamists are there and they trained there. Yet you also stated that they are everywhere. Should it not follow that we should invade everywhere? They certainly can train anywhere.
What you don't realize is that every "terrorist" you kill creates three more: his kids, his friends, his neighbors. I would ask you what your master plan would be to so quickly win the world wide war on terror, but I know you won't have a plausible answer.
Hint: No amount of globe-trotting terrorist hunting will ever destroy a political philosophy.