I think you're the one missing the point. While the U.S. military's record in the past 100 years or so is not unblemished, it has unquestionably been one of the greatest forces for good on the planet. Absent the defensive shield provided by the U.S. military:
- At some time between 1945 and 1950 the USSR likely would have moved the Iron Curtain all the way to the Atlantic, and quite possibly to the west coast of Britain or even Ireland. Practically anyone who lived under Communist rule in Central- and Eastern Europe would agree that this would have been a Very Bad Thing.
- In the summer of 1950 the Korean peninsula would most certainly have been reunited under the Kim Il Sung regime — this damned near happened anyway, when the U.S. and ROK forces were nearly pushed into the sea at Pusan — and the South Korean economic miracle would never have occurred, to say nothing of the fact that the North Korean gulag would be that much larger.
- Japan probably would have rearmed, and who knows what that would have led to.
Oh, and absent the freedom of the seas heretofore provided by the United States Navy, the world's economy would look very, very different.
As to "smart policy and liberal principles," those are certainly important. But as President Obama said in his Nobel Peace Prize acceptance speech, nonviolence wouldn't have stopped Hitler's armies.
Disclosure: I'm biased — I'm both a veteran and the son of a career U.S. military officer.