Distinct historical backgrounds of North American and Central American immigration.
Distinct racial relations and attitudes result.
Different migration patterns.
Mexican Americans as minority in USA:
Historical: Conquest and annexation by the United States of Mexican territory in 1800s is historically analogous to conquest of American Indian lands in earlier centuries.
(+ Minority status in Central America: American Indians were often enslaved or otherwise exploited by Spanish colonizers.)
Racial / ethnic: Partial American Indian descent of many Mexican Americans associates them with American Indian minority status.
Traditional extended families (however fragmented) with traditional gender roles are more common in minorities than in dominant culture.
Brevity of childhood, beginning work early to support family, and early child-bearing ("age at first birth") are contrary to dominant culture's extended childhoods, but this may the result of class more than ethnicity.
Mexican Americans as immigrants to USA:
Historical: Since most of "New Spain" became part of the USA, Mexican immigration to former parts of Mexico and other parts of the USA has taken place in several waves, responding to unrest in Mexico (e.g., the Mexican Revolution of the 1910s, the Mexican debt crisis of the 1980s-90s, NAFTA in 1990s) and to need for cheap manual labor in the USA, especially during war-time (e.g. Bracero program during WW2).
Racial / ethnic: Intermarriage is a primary driver of assimilation. Since intermarriage is inherent in the Mexican American or mestizo identity, Mexican Americans appear to adapt easily to intermarriage with other ethnic groups within the USA.