Mexico dwarfs South America: about 1,962,279 km² km² against 17,840,000 km² km². At true size Mexico is about 9.1× larger — the whole of South America fits into Mexico roughly 9 times.
The old Mercator map treated both about equally (1.2× vs 1× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Mexico fits 9× into South America.