U.S.A.
Canada
Mexico
Great Britain
Norway
Germany
Denmark
Austria
Greece
The Netherlands
The Czech Republic
France
Singapore
Indonesia
Australia
New Zealand

Japan if you want to count multiple stops in the Tokyo airport. China if you want to count Hong Kong despite the fact that I visited while it was still an English possession. I'm probably forgetting some others as well. Switzerland and Sweden are incredibly likely, but I can't remember for sure.