And there were massacres by the South Vietnamese equal in scale.
Given the circumstances around its discovery, it is very probably the My Lai was indeed the tip of the iceberg in terms of US crimes. I'm from a country which has an active Communist insurgency - don't have to dig too deep to understand what happens when, for example, "a village is freed from Communist control and 18 insurgents eliminated."
This was just last week. Not going to include extremely grisly stuff that came out some years ago when the press clampdown in Naxal areas was less absolute, and the pattern is almost always the same: triumphant release that terrorists were eliminated, a week later, locals dispute that characterisation.
The initial publicity about My Lai was exactly the same, with public congratulation for the perpetrators for eliminating VC. The difference was the heroism of one man. It is very logical that there were other incidents that will not be known.
The US won the Cold War. It "won" the Vietnam war - the dominoes stopped falling, while it simultaneously helped Indonesia liberate itself from Communism at the cost of 3 million lives. Scrutiny from anonymous people online is a small price for ruling the world.