Not counting places I’ve only been in the airport or driven through:
States and similar thingies: Alaska, California, Connecticut, Delaware, Florida, Illinois, Maryland, Massachussetts, Minnesota (I think – some of the childhood vacation memories are fuzzy), New Hampshire, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island, Washington, Virginia, Wisconsin (I’m pretty sure), and DC.
Foreign countries: UK (all four of the major parts), Ireland, Spain, France, Belgium, Netherlands, Germany (briefly), Austria, Czech Republic, Hungary (also briefly), Switzerland (ditto), Italy, Canada, Mexico, Bahamas, Dominican Republic, Fiji, Cook Islands, New Zealand.
Hoping to add Australia, Thailand, and Cambodia next year.