This page suggests that there is very good recording and details on past trips, so we should probably be able to rely on this page: https://en.wikipedia.org/wiki/List_of_presidential_trips_made_by_Joe_Biden_%282023%29
Flying over, cruising, etc don't count, he has to actually be there.
The timespan of the claim begins on inauguration day, 2025 and goes until the end of the year.
The person doing the visiting must be the president - at first, whoever is inaugurated, but if the president is replaced, their successor counts for country visits. So there is always a person who can do the visits; if the president for example, quit and was replaced by the VP, the market would continue.
Interpretations:
afterlife means the president passes away, but we will continue with the replacement from that point
coma means they have a coma while being president
History
In his first three years, Biden made these 23 international trips. Note that COVID caused a severe and long drop.
And in just 2023 here are the states he has visited so far:
Here is what ChatGPT thinks the countries the wikiepedia page mentions are:
Mexico
Germany
Poland
Ukraine
Canada
United Kingdom
Ireland
Lithuania
Finland
India
Vietnam
Israel
It's slightly strange that they don't split them out as much as they do the states.