Firstly, I'm not sure we're reading the same article, but by my summary count, the total death toll for all combined US war crimes detailed in that article isn't much more than 10,000.
Next, the veracity of some of those claims is questionable at best.
Finally, it should be noted that the Tiananmen Square protests, were, in fact, protests. This was not an action against civilians during war time, this was an action taken by a government against it's own citizens who were protesting.
Is killing unarmed soldiers or civilians in war time justified? Generally no. But it's a different type of crime when you're in the middle of a war zone. Humans don't deal well with the insane nature of war, and so they do horrible things. That's not an excuse, mind you. But I think collateral damage in a war and civilian casualties in a war zone are very different scenarios than Tiananmen Square.