U.S. Government: Interfering Busybody or Protector and Stablizer?

Anne of Idaho writes:

It should be possible to remove ourselves from the habit of interfering in the internal policies of other nations while not giving up our role as protector and stabilizer of general areas of commerce in the world. Think of it this way: police action can be limited to protecting citizens in the streets (i.e., in public) but not invading homes and businesses (with or without warrants).

Our federal domestic policy of interfering in the minutest aspects of personal life (what we can eat, say, teach) is mirrored in our concomitant policy overseas of thinking we have the right to oversee the lives of foreigners.

A good parent knows how to maintain order without stifling freedom of thought and action. A “good nation” can and should do the same.

But a nation is not an entity in and of itself. It is a composite of millions of people of all ages and beliefs and agendas. Our ability to turn “nation” into an abstract whole has historically been of questionable service to the pursuit of peace and happiness. But the greater error will be in the abstract concept of “one world.”

People is plural.

Agree on all points.

Question: What if we learn that foreign terrorists are plotting and planning in private homes or the back rooms of private businesses of their nations? Do we have the "right" (or obligation) - with or without state or legal authorization - to disturb them and try to prevent their crimes before they hit the streets?

Question expanded to our dealings with nations: What if we learn that weapons are being developed and/or terrorists and murderers are being trained and motivated in the caves and compounds of certain countries? Do we attempt to preempt? Or do we wait for the crimes to be committed, and then try to track down the perpetrators, and hope that our success in doing so will prevent other crimes?

Should the liberty of a person, group, or nation be allowed (have the right to) exist right up until a crime is committed? Or is one's liberty subject to limitation as soon as one begins actively planning to infringe upon the liberty of another?