Someone needs to take out Machiavelli or otherwise prevent him from writing The Prince while we’re in the past. Might not do anything but it could fix a lot if it does
Yes. I read The Prince and I think Machiavelli's reputation as malevolent and scheming is undeserved. Perhaps he shocked the sensibilities of some by saying the quiet part out loud, but it would be foolish for either a ruler or his subjects to be unaware of that quiet part due to misplaced idealism. This remains true in the present day.
Edit: I assume that you know this, but I thought that a reply to you was a good place to say it to others.
The Chronicles of St. Mary's is an entire series of historians "investigating historical events in contemporary time." Don't call it time travel. They don't like that term.