My others are Denmark and Andorra.
We’ve already had plenty of that, thank you so very much.
I actually visited from both sides (on a trip from Pyongyang and later, a trip from Seoul). It was interesting that the US and South Koreans were much more paranoid about the place than the North Koreans… it was a much more relaxed and “rule-free” visit from the northern side. Personally, I don’t think being in a country counts unless you have gone through immigration/customs (which was easy in Pyongyang).
If you get the chance, I’d highly recommend visiting Pyongyang - weird and fascinating place.
Does Bermuda count under UK? if not, add another other, brother!
Canada
Costa Rica
Belize
Mexico
Honduras
France
Italy
Monaco
Vatican City
US
are mine.
I want to add at least Greece, China, Germany, the UK, Ireland, Russia, Israel, Australia, Japan and an African country before I die.
My others were Nicaragua, El Salvador, and Panama.
My others are Ireland and Norway.
I’d love to visit North Korea one day, but I wonder if it will become possible in my lifetime (visit properly, not just through those regulated tours).
Do you mean San Marino?
As one of the Channel Islands, it was lumped in by the OP with the UK and the Isle of Man. It is officially a British Crown Dependency, and thus not part of the United Kingdom. However, the UK is responsible for the Bailiwick’s defense, and there are other quirks in the legal connections of Jersey and the “mother country”.
As for me, I was “born in the USA” and have lived all my life here, but have taken several trips to Canada. My third country is Cuba. When I was a college freshman, I spent two weeks there on a tour, with multi-night hotel stays in Havana and Cienfuegos.
Oh yeah, and Brunei (a few months later and I’d have likely needed to add Kyrgyzstan and Turkmenistan in the Others)
In order:
United States
Japan
Mexico
England
Belgium
Italy
Austria
Germany
Denmark
Sweden
Canada
Of those listed:
The US
Mexico
Israel
The UK
France
Italy
Egypt
Bulgaria
Romania
Turkey
Colombia
India
The Philippines
Other:
Ireland
The Vatican
Palestine (The West Bank)
Macedonia
Bosnia & Herzegovina
Albania
Others for me are:
Vatican, Aruba, Jamaica, Barbados, St. Lucia, St. Maarten/Martin, Curacao, Bahamas, Cayman Islands, Antigua, and Martinique
My ‘Others’ were Fiji and New Zealand. I’ve also been to Aruba, which is kind of Dutch, and Gibraltar, which is UK-ish.
Hey, how about principalities? Monaco, Andorra, Vatican City?
Also Luxembourg, New Zealand, Laos, Ireland, Singapore, Slovakia, Denmark, Latvia, Lithuania, Estonia, Finland, Rwanda, Swaziland, Lesotho, Namibia, Botswana, Malawi, Bolivia, Paraguay, Uruguay, Yugoslavia.
I’m sure I forgot something. In any case, 68 countries and principalities. Does Tahiti count for anything?
Now I’m pretty sure I’ve been to every country in the Balkans, but it was called Yugoslavia back then. If you go by that criteria, I’m probably up to 71.
Canada, France, Germany, Greece, Italy, Mexico, Switzerland, UK, Vatican, and I’ve lived in the USA my whole life. If airport transfers don’t count, then drop Germany (Frankfurt’s airport is the smokiest place I’ve ever suffered through) and Switzerland.
Taiwan and Thailand will be next.
Five.
On the list that I marked: France, Belgium and Mexico.
On the list that I forgot to mark: United States 
Not on the list: Luxembourg.
Been to several not listed. Strange that Honduras and Guatemala are listed but not Nicaragua (been there).
I ticked Germany, but back then I was in both West Germany and East Germany. And I ticked the Czech Republic, but at the time it was Czechoslovakia, although the parts I was in are now the Czech Republic; did not venture over to the Slovakia side.
I’ve been to 21 of those, plus a number not listed:
Bosnia
Croatia
Slovenia
Macedonia
Slovakia
Turkmenistan (just a brief crossing into the country from Uzbekistan–barely counts)
My other is Nicaragua
My others:
Liechtenstein
Vatican
Slovenia