How are the Mexican flag and the US flag different?

The US and Mexican flags are different designs and they mean different things.

The US flag is symbolic of the original 13 colonies, and of the current number of states in the Union.

The Mexican flag is symbolic of the foundation myth of the Mexica (Aztec) tribe, who are said to have founded their great city where they saw an eagle perched on a cactus plant with a snake in its mouth.