Kazakhstan is clearly the larger of the two: about 2,712,747 km² km² against 1,962,279 km² km², roughly 1.4× at true size. Drag one onto the other on the map above to feel the gap.
Kazakhstan 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 1.4×.
The old map muddied it further: Mercator inflates Kazakhstan about 2.3× and Mexico about 1.2×, so on a Mercator-style map this pair appears 2.6× apart instead of the true 1.4×.
Mexico fits 1× into Kazakhstan.