Closer than most people guess: Mexico (1,962,279 km² km²) is only about 5%% larger than Sudan (1,863,027 km² km²).
Mexico sits in North America, Sudan in Africa. On the old Mercator map the latitude gap distorted how large each felt beside the other; at true size the answer is simply 1.1×.
The old Mercator map treated both about equally (1.2× vs 1.1× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Sudan fits 1× into Mexico.