re: The worst wars to be a US soldier in

I'd pick the Civil War and World War 1. Disease during the Civil War and soft lead projectiles with low muzzle velocity made for some horrendous wounds that resulted in death or amputation. There were no modern medevac and surgical facilities like they had in Vietnam, which would have mitigated much of the suffering that occurred during the CW. There was also a very unpopular draft of Union soldiers during the Civil War that resulted in violent riots in New York City.

World War 1 wasn't much better than the Civil War in some respects. You had outdated tactics that were similar to those of the Civil War, but deadly accurate artillery, machine guns, other advanced, modern, weapons, and poisonous gas inflicting gruesome casualties. Not to mention being chewed to pieces while entangled in barbed wire. Wet, rat-infested, trenches (not unlike what was seen in the latter stages of the Civil War) would not have been any fun, either.