Day 3- Rome
If you do nothing else, do the Colosseum. It is incredibly impressive, and it is well worth it to research the historical context to get a feel for the place. The Vatican was amazing,but pretty much the definition of overkill. The Pantheon was wonderful on the outside, but the Christianised interior was kind of sad.
Day 4- Florence
I don’t know why people don’t like American tourists. They’re generally friendly and tip well. Me and my Fellow Spawn talked to an American couple on the train, and they were really nice, even if they were Republicans. It seems that American tourists support each other, like helping with directions and taking photos for each other. Doesn’t seem like objectionable behavior…