Actually the cyphers would be that the USA lost:
-350.000 men in WWI
-300.000 in WWII
WWI was much bloodier. And let me tall you this, buff. It is totally unwise to compare WWII with Vietnam. You can't say that Vietnam lasted more than WWII and had less casualties. First, the number of men involved were not the same. Second, the nature of fighting was very different, the terrain, the weaponry, the tactics and the enemy.
And of course USA did not win that war. They didn't achieve their strategic goals and lost many men, expent too many resources and after Vietname the US Armed Forces were pitiful... in a very bad shape, as well as the country's morale. Maybe the USA could bomb Hanoi freely with their B-52s and take some villages, but they could never whipe the Viet Cong out of the forests...
That is not a victory, and in case it would be a victory (which is NOT) it would have been a phyrric one...