Good choice! Italy (my homecountry) is very diverse, it's got big cities and countryside little towns, beaches and mountains. If you like art then, by all means choose the "tourist route" Venice-Florence-Rome, the "can't miss" towns which will be more than enough for a week (although I recommend 10 days). They are easy to plan for since you can surely find a guide in the USA before hand.Go either in May or in October (best for weather and temperature).
If you are looking for a more seclusive, romantic, relaxed time then I would recommend Capri or the Riviera Ligure (up north towards France - Portofino, Monterosso, Vernazza etc..). I have soo many more places to recommend (oh my gosh Naples, Tuscany, Sicily and the Lipari Islands, Puglia etc...they are ALL unbelievable), so if you have an idea on what you'd like to do, pm me, I'll be glad to help.