The problem isn't war, so much as unjust illegal wars. The number of dead doesn't determine whether a war was just or an act of unprovoked aggression.
Vietnam and Iraq were unprovoked wars of aggression. The people responsible should have faced war crime charges.
WWI and WWII were not started by the US, but effectively they were ended by the US. So I give the US credit for ending those two wars, not starting them.
The Vietnam war escalated as a result of a lie:
30-year Anniversary: Tonkin Gulf Lie Launched Vietnam War
The 2003 Iraq war started as a result of a series of lies regarding Iraq's WMD capabilities and intentions as well as Iraq's involvement in the events of 9/11.
WWII also started as a result of lies and manipulations just like Iraq. But in that case it was German leaders who lied to and manipulated their people.
If a political leaders lies and misleads their country into an unprovoked war, then the people have an obligation to hold that leader responsible for the consequences of their lies and manipulations. I am disappointed that the American people have still not held the people responsible for the Iraq war accountable for their actions.
Also while I have written on many occasions that George Bush Jr. is a war criminal for lying about Iraq's WMDs and links to 9/11, I also believe that its possible that he maybe a victim. His advisers may have used misinformation to manipulate Bush into starting a war. However as CiC, he is ultimately responsible for every single person who died as a consequence of that war, (Iraqi, American...)