Here are some suggestions, keeping the same general route as you have planned:
I would try to fly into Toronto, Canada. From there, you can drive south, through Niagara Falls, and cross Upstate New York. Upstate New York is a beautiful area. You can cross and drive up to any number of seaside towns in Maine. Portland, Maine, gets a lot of press for being a quintessential New England fishing village. From there, you can drive south to Boston. Boston has a ton of history, and I recommend visiting Harvard University and Harvard Square while there. From Boston, you can visit Newport, Rhode Island. The former summer getaway of the NYC wealthy.
From Newport, you can work your way across Connecticut, which is filled with charming small towns and fishing villages. That will lead you to NYC. Go see Times Square, but only to say you've seen it. There are many other, more worthwhile things to do in the city than the normal touristy things.
From NYC, drive south to the town of Princeton, New Jersey. Princeton is a very charming little town, and is home to a wonderful University. I would then drive south to Philadelphia, another town filled with history and historical sites. From Phily, you can drive south to Washington DC. Make sure to visit Mount Vernon while in DC. It is George Washington's home. I'd then drive across Virginia and visit Charlottesville, which is home to the University of Virginia, and visit Monticello (Thomas Jefferson's home). From there, you can drive south and visit Pinehurst, North Carolina.
From Pinehurst, I would go to Charleston, South Carolina, and Savannah, Georgia. They are two historical, beautiful small cities.
From Savannah, you can drive around and see a lot of the small towns in the deep south. You can also drive south through Florida to Miami. Miami will give you a sense of a completely different culture in America.
From Miami, I would fly into New Orleans. New Orleans is distinctively itself. It is a great town, and a must visit. You could then drive from New Orleans to Houston, Texas. My advice would be then to fly to Seattle, Washington. The Pacific Northwest is home to some of the finest that mother nature has to offer. You could drive down through Portland, San Francisco, the Monterey Peninsula, and LA.
I hope that's only semi-confusing. I'm not sure that Kentucky and Tennessee have enough to offer to warrant you driving as far out of your way as you would be going to do so.