It turns out I have visited 11, or 21% of the states in the U.S.A. (counting, as this map does, DC as a separate "state").
I can thank many business trips and flight transfers to count for many of those. In the future I should travel alphabetically, to make tracking easier.
create your own visited states map
or check out these Google Hacks.
Map generator, US States, Travel log, meme