I have never written this list before so I might have missed a couple.
About 40 of the US states
Puerto Rico
Hawaii
Canada
Bermuda*
Nassau*
Mexico
Panama
Peru*
Virgin Islands
England
Scotland*
France
Spain
Netherlands
Belgium
Denmark*
Finland*
Germany - both
Poland*
Hungary*
Austria
Luxembourg
Lichtenstein
Italy
Ethiopia*
Somalia*
Philipines*
Japan
Thailand
Burma*
Cambodia*
Vietnam
Laos*
My only planned trip to Russia was called off at last moment.
The ones with asterisk were one-time visits only.
My favorite country so far is Laos.
None of these were pass-throughs. [I don't count overnights in Alaska, Taiwan, Hong Kong or Iceland] The shortest was probably Luxembourg or Lichtenstein for two days (very small country). The longest was Germany for 4 years, next Laos for 6 weeks.