Interesting start to the story. But I don't think the history is accurate. As I understand it, at that time, there was a Kingdom of Italy, part of the Holy Roman Empire. However, that included only northern Italy and there were separate imperial fiefs (dukes, princes) in each of the individual city-states of northern Italy, rather than a single King.
Also, I'm not sure Americans shortly after the Revolution were friendly towards European royalty.
I'm not a historian, maybe someone else could provide a more accurate information.