Charleston, SC. Perfect 4-5 day trip. Lived there for five years...after extensive world travel, still my favorite city in North America.
Conde Nast named it the top US city for a reason.
If you end up going there, PM me for recommendations.
EDIT: too hot in SC in July.
Go to Asheville, NC. Rent a car, drive the Blue Ridge Parkway. Beautiful...one of America's most beautiful spots. Tons of low key but high brow restaurants. Best chocolate shop I've seen outside of Europe (French Broad). Best Spanish food in the country (Curate). Amazing place!!