The conventional political boundary runs through the Darien Gap on the Panama-Colombia border, which places almost all of Panama within North America. Some geologists instead draw the physiographic line farther north, at the Isthmus of Tehuantepec in Mexico, treating the rest of Central America as a transitional zone rather than as part of North America proper. The two conventions, political and physiographic, answer different questions and disagree by roughly two thousand kilometers.
What would resolve this A single agreed convention for whether the continental boundary follows political borders or physiographic features would settle which line applies; no new fact discovery is expected to close this on its own, since both conventions already agree on the underlying geography.
OpenPhysical geographyNorth America (Wikipedia)