but if a nation's legacy is exclusively the sum of blood spilled, I ask you to show me one that is not utterly drenched in evil.
You forgot to answer that!
And would it be reasonable to discount Isaac Newton's contributions to mathematics because "its not like nobody would have figured it out without God..."? Actually doing the thing matters.
I think you're missing the forest for the trees. The ideas and ideals the American Revolution brought to the world (not always practiced as preached) are absolutely world shaking and inspiring. While I know 'america bad' is fashionable, we really should think about what the American Revolution, where tens of thousands fought and died for the first war ever fought for the unalienable rights of all mankind, philosophically meant to the world.
This is a nation not founded on a shared ancestry, a shared religion, or a shared history, this is a nation founded on some of the most amazing Ideals in human history, even if they're not lived up to. Neither fascist dishonestly abusing the flag to destroy its meaning nor flippant doomer will make me not love Life, Love, and Pursuit of Happiness, and I will celebrate and aspire to the ideals this country was founded upon.
I encourage anyone and everyone to watch Ken Burns' civil war, you just might have your mind expanded!
https://www.pbs.org/kenburns/the-american-revolution (Also give PBS a couple bucks, they need it)