Judge, Charles Krauthammer gave a speach regarding the US future in world affairs. He gave a pretty good argument as to when and why we should draw the line:
"Moreover, democratic globalism is an improvement over realism. What it can teach realism is that the spread of democracy is not just an end but a means, an indispensable means for securing American interests. The reason is simple. Democracies are inherently more friendly to the United States, less belligerent to their neighbors, and generally more inclined to peace. Realists are right that to protect your interests, you often have to go around the world bashing bad guys over the head. But that technique, no matter how satisfying, has its limits. At some point, you have to implant something, something organic and self-developing. And that something is democracy.
But where? The danger of democratic globalism is its universalism, its open-ended commitment to human freedom, its temptation to plant the flag of democracy everywhere. It must learn to say no. And indeed, it does say no. But when it says no to Liberia, or Congo, or Burma, or countenances alliances with authoritarian rulers in places like Pakistan or, for that matter, Russia, it stands accused of hypocrisy. Which is why we must articulate criteria for saying yes.
Where to intervene? Where to bring democracy? Where to nation-build? I propose a single criterion: Where it counts.
Call it democratic realism. And this is its axiom: We will support democracy everywhere, but we will commit blood and treasure only in places where there is a strategic necessity--meaning, places central to the larger war against the existential enemy, the enemy that poses a global mortal threat to freedom.
Where does it count? Fifty years ago, Germany and Japan counted. Why? Because they were the seeds of the greatest global threat to freedom in midcentury--fascism--and then were turned, by nation building, into bulwarks against the next great threat to freedom, Soviet communism.
Where does it count today? Where the overthrow of radicalism and the beginnings of democracy can have a decisive effect in the war against the new global threat to freedom, the new existential enemy, the Arab-Islamic totalitarianism that has threatened us in both its secular and religious forms for the quarter-century since the Khomeini revolution of 1979."