Does American intervention make things safer or more dangerous?

“Ever since the Munich agreement and Pearl Harbor, with only a brief interruption during the decade after the Tet offensive, there has been a consensus that if Americans did not draw their defense perimeter far forward and confront foreign troubles in their early stages, those troubles would come to them at home. But because the United States is now the only superpower and weapons of mass destruction have become more accessible, American intervention in troubled areas is not so much a way to fend off such threats as it is what stirs them up.”
–Richard K. Betts, “The New Threat of Mass Destruction”, Foreign Affairs, Jan./Feb. 1998