Governments have to make choices about risks to their stability. This is a basic self-preservation sort of thing. In the U.S., we (the general public) like to think we (the government) have a balanced policy which doesn't trample on the civil liberties of citizens or unduly interfere with other countries.

Of course, this is a false perception of the benevolence of our government.

The U.S. has a long history of invading and killing people in other countries for a variety of reasons. The U.S. went into the Phillipines to Christianize the people. (At least, that was one of the public reasons.) Most actions in the latter half of the twentieth century were to combat the spread of communism. Or, rather, to block the influence of Soviet Russia and China, which were arguably not very communist at all.

The most recent rational for inserting troops/influence has been as a preemptive strike to keep terrorists/ radicals/ Islamists/ Communists/ dictators (not ours) from gaining control and in order to unselfishly control/manage the oil/ resources/ economy/ strategic location for the good of the world.

It's a funny thing about preemption: If done too soon, it can look a lot like unwarranted overreaction against non-threatening countries and people. This is why, at events where Pres. Bush speaks or appears, there is a massively overdone effort to keep dissenters far away from the main area. Often this includes overuse of force where it is not necessary. This is the preemptive principle gone ugly and paranoid beyond reason.

I don't think too much preemption is a very good basis for sound foreign policy or crowd control of peaceful demonstrators.