Mongolia dwarfs North America: about 1,560,428 km² km² against 24,710,000 km² km². At true size Mongolia is about 15.8× larger — the whole of North America fits into Mongolia roughly 15 times.
The old Mercator map treated both about equally (2.2× vs 1× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Mongolia fits 15× into North America.