Jihadists returning to USA are not the big problem.

[Mack Knife]

The big problem is the ones who never leave the USA in the first place. They are already here and do not go overseas so trying to track them at our borders is useless.

It is the enemy within we need to worry about, not those who want to come through our borders.

[Retroit]

But isn't the reason they are leaving is so they can get more training and indoctrination, which makes them more of a threat when they return?

[brokensky]

I think maybe the situation of leaving and screening someone when they return is what the OP is referring to. We have a chance of screening folks who re-enter the USA, but it is possible the "home grown" terrorist who never leaves the country will never be identified, especially if they have been "groomed" by other jihadists for years while living a supposedly "normal American life" here in the USA.

It doesn't take a lot of training to figure out how to shoot a gun into a crowd.

[Retroit]

So are you saying (or is the OP saying) that we should be more concerned about the average American who could possibly be a terrorist than we are about someone who goes to the Middle East for a few weeks and returns?