Closer than most people guess: Iran (1,622,847 km² km²) is only about 21%% larger than Mexico (1,962,279 km² km²).
Iran sits in Asia, Mexico in North America. On the old Mercator map the latitude gap distorted how large each felt beside the other; at true size the answer is simply 1.2×.
The old Mercator map treated both about equally (1.4× vs 1.2× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Iran fits 1× into Mexico.