After ten books I can do some statistics! Behind the cut to spare you if you don't care ;)
Round the world in books:
USA: A vintage Affair, This Dark Horse, Mrs. Kaplan and the Matzoh Ball of Death
UK: Sweet Disorder, A Rose in Flanders Fields
Germany: Hätte, Hätte Fahradkette (it's non-fiction so you can sort of argue if that is ever set anywhere but the author is German and brings much of his own life-story in it so that counts)
Belgium: A Rose in Flanders Fields (it's set in two places and both are pretty important so again: it counts ;))
No difference in the US-states to the last time. I have no clue where Mrs Kaplan is set and am not sure if it is ever mentioned.
So:
Real Countries visited: 4 (US, UK, Belgium, Germany)
US - States visited: 2 (California & Georgia)
Fantastical countries visited: 3 (Land of the Niflungs, Gothic Italy, Discworld)
And because that is so much fun:
With books through time:
Castle of Otranto is supposedly set somewhen during the cruisades so I put 11th century
Sweet Disorder is a Regency Romance
A Rose in Flanders Fields during Wolrd War I
A Vintage Affair is just the first contemporary novel I read this year, if I would add everyone it would get pretty crowded pretty quickly