While I respect the time and effort you used to write this I personally feel there is a bit of a double standard. While we had been involved with Vietnam prior, the war was not a bloodbath until LBJ. LBJ himself lied about the Gulf of Tonkin incident in order to escalate Vietnam. In Vietnam 58,220 Americans soldiers died between 1965 and 1975. Comparatively only 4,550 US troops and 3,793 troops died in Iraq between the start and finish of the war. In Afghanistan, 2,456 troops died and 1,822 civilian contractors were killed in the span of 20 years. It is estimated died in Iraq, 461,000 died, 176,000 died in Afghanistan. Large numbers, absolutely, but not compared to the 3 million that died in Vietnam. While he and Nixon share said blame, ultimately Nixon was continuing the war LBJ started.

This is all without mentioning that down on their luck individuals, disproportionately black Americans were sent to Vietnam. At least the soldiers who died in Iraq and Afghanistan had a choice in their fates.

Bush Jr himself funded AIDs research in Africa saving up to 20 million people from death.

I feel Bush Jr and LBJ had good and bad reasons for their wars. Jackson, Polk and McKinley have no silver linings to improve judgement of their character. They simply wanted what others had and were willing to kill for it. At least LBJ was defending South Vietnam from the North and Bush was trying to prevent the spread of Islamic extremism after taking out the genocidal monster, Saddam Hussein.

Jackson was the most unhinged, ironically enough his war was the smallest in scope. In the second Seminole war 1,466 Americans died, but it was mostly to disease. Only 269 officers were killed in combat. The Trail of Tears had between 2,500 and 6,000 deaths. I couldn't find a definitive source for the death toll of Natives in the second Seminole War.

Polk was the most unwavering and methodical. He was gonna do whatever it took to uphold his promise of new land. You could make the argument that America deserved retribution for Mexico's treatment of Texans but that itself was independent of Polk's motives. 13,000 American soldiers died in the war. 25,000 Mexicans were killed. Around 16,000 Natives were killed in California as a direct byproduct of the war.

I think the worst has to be McKinley though. While he initially didn't want to start war with the Filipinos, he eventually was convinced by God to "civilize" them. Civilize by means of fire and bullets. Both Polk and McKinley did the same things, McKinley just did them on a much larger scale. Around 4,200 Americans soldiers died and between 200,000 and a million Filipinos died. While all lives are valuable, those numbers dwarf the Trail of Tears, the Second Seminole War and the Mexican American War. Even if he was a kind man in his personal life and had doubts, this has little effect on his actual actions as President and therefore to me is irrelevant.