Viruses and terrorists have something in common: if you don’t stop them overseas, you have to crush them at home. Which is the better approach?
Neither is perfect. The problem with operating abroad is that you don’t know the terrain, and you have to work with local partners who are generally far from perfect. The problem with creating “Fortress America” is that the border is the last line of defense, and you may have to impose restrictions on freedom of movement that are obnoxious to the American public and are largely unnecessary.
The best approach combines elements of both, and adapts to facts on the ground on a case-by-case basis. One thing is for certain; simply withdrawing from the world without considering the consequences is a recipe for disaster at home.