Wii launched in Mexico same time as USA, 360 launched launched in Mexico 3 months after it launched in USA, and PS3 didn't launch until 9 months after USA. Using NPD & IDG data for the period when each console was available in both USA & Mexico we get:
360:
USA (NPD Feb 06 - Dec 07): 8,307,000
Mexico (IDG Feb 06 - Dec 07): 550,000
Mexico % of USA: 6.6%
Wii:
USA (NPD Nov 06 - Dec 07): 7,417,000
Mexico (IDG Nov 06 - Dec 07): 220,000
Mexico % of USA: 3.0%
PS3:
USA (NPD Aug 07 - Dec 07): 1,635,000
Mexico (IDG Aug 07 - Dec 07): 60,000
Mexico % of USA: 3.7%