We have a volunteer military, not a drafted military like WW2
We'd also have massive anti-war protests rather than a few loons. For all their talk about caring for the Vietnamese people, most of the anti-Vietnam War protesters really just didn't want to go to war (you'll notice that their concern for the fate of the Vietnamese people evaporated once the draft ended -- most don't know or care what the North did when they took over).
I also don't think we'll put the War on Terrorism into the WIN column until we are ready to invade, encourage a coup, or bomb out of existence Iran, Syria, Sudan, Somalia, Lebanon, and North Korea. And the problem with at least some of them has more to do with global politics than the size of our military. Sadly, it's probably going to take a very large WMD attack on the United States before people treat it like a war.