That's got to be one of the most poorly framed questions I've ever seen, not only here on the flip, but in general. Simple logic and generally accepted facts refute it.
Not all Americans were eligible for military service. Only those between 18 to 25, I believe.
During the Vietnam War era, the U.S. military drafted 2.2 million American men: https://cherrieswriter.com/2019/08/11/the-military-draft-during-the-vietnam-war/
Why don't you ask your question to the families of the 58K+ who died?
What do you hate the most about America?