Which is more efficient for the US: to focus on their own problems or to interfere other's business?

Depends on your definition of efficient, I guess. The rich folks and corporation who own this country and government need to get more wealthy, the most efficient way is to take it from other countries (at the expense of this country). That's working out for them so I guess that's efficient.

It would be great if America could focus its resources of every kind on itself. But if we pulled our foreign aid and technology from all the places we "interfere" in most of them would simply implode. All those places we interfere in should stop asking for our help.

That would be okay with a great many Americans who, like myself, believe we should FIX AMERICA FIRST, stop immigration altogether for a few decades, deport every illegal we can round up, seal our borders, tell OPEC to eat their oil, and use America's resources, money and power to further enhance American exceptionalism.