Today the U.S. underwrites the defense of wealthy nations across the globe. Washington should stop using the Pentagon as a global welfare agency. Uncle Sam at least should charge for his defense services, as Donald Trump has suggested. America shouldn't be defending its rich friends for free.
The terrorist attacks of 9/11 demonstrated that the Department of Defense is not well-prepared to defend Americans. For that reason Congress created a new agency, the Department of Homeland Security. The Pentagon devotes much of its resources to projecting power abroad to defend other, mostly wealthy nations. In most of these cases America has no important, let alone vital, interests at stake.
The obvious answer is to stop doing stupid things, as President Barack Obama preached but failed to practice. Washington should allow allies and friends to protect themselves. They have the wherewithal and incentive to do the job; government welfare creates dependency among foreign as well as domestic recipients.