Today is Cinco de Mayo, a Mexican holiday that is celebrated more in the United States than in its country of origin: a Mexican-American holiday more than either a Mexican or American one. How can Mexican-American-ness be expressed through flags? Most commonly, of course, the Mexican flag is used for this purpose, often in conjunction with the US flag.
But here are some designs for merged or distinctive Mexican-American flags.
The text reads:
The cause is holy and God will protect it.
Long live Our Lady of Guadalupe,
Death to bad government,
Death to the Spaniards and the British!
Long live independence!
Long live the Mexican-American United States!
Portland Flag Association 
A nice collection of Mexican-American flags.The flag by artists Jorge Rojas and Diego Aguirre is the simplest and least complicated design that is BOTH American and Mexican.