The basis of this is flawed because the "peace" started several decades before the 90s, and completely neglects the role of Mutually Assured Destruction in creating that peace. If anything, America's position was detrimental to that peace because it allowed it to wage its own unilateral wars.

This continues to be the case now. The main difference is that in the 90s, the opposition to Vietnam was still fresh enough in the average American mind. I suspect what we're seeing now is the effect of that memory fading.