France is a MAJOR ally of the US. They’re our OG ally. It’s also an important democracy in the community of those, and they play an important part in defending our shared interests. The potential incoming French government is seriously unsympathetic to any of these alliances, democratic values, etc.
In other words, an old friend may be about to turn Mr. Hyde on us. There’s not much we can do.
It doesn’t for the presidency. There’s just a line of succession.
Other positions often have special elections for absences (deaths; resignation), but it’s also wildly inconsistent because the states mostly all do it completely differently.
Speaker of the house is second in line, and when a House member leaves office mid-term, a special election is held. Theoretically, any house rep could resign and a new one elected, that person made speaker, then when the president and VP resign, that person will be acting president. The only limitation is that the house member has to come from a specific district.