Mexico dwarfs Oceania: about 1,962,279 km² km² against 8,600,000 km² km². At true size Mexico is about 4.4× larger — the whole of Oceania fits into Mexico roughly 4 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 4× into Oceania.