Torog, how the hell could America have liberated 1 billion people last century. Let's see... wars that America was in last century...

1st World War: America liberated no one. No one got liberated at all.
2nd World War: Germany, Japan and Italy were liberated from dictatorships, none of them directly though. I could have sworn that there were a lot of other countries in that war who put a lot more effort in the America did. Oh well...
Korean War: No one liberated. Many killed.
Vietnam War: America poking it's nose in to stop the nasty commies. No one liberated. Many killed.
Gulf war: No one liberated

Maybe you are counting the Cold War? Firstly, as with the 2nd World War you were not the only country involved by a long shot, secondly the USSR was not liberated, America just kept threatening it (and the entire world) until it collapsed due to a failing economy, brought on by itself, not by any brave Americans.

At the end of the last century there were 6 billion people in the world. Are you saying that America "liberated" 1/6 of the entire world's population? With is own 200-and-something million people?