The main difference between history classes in the U.S. and Mexico, according to the provided options, is best captured by the statement:
In Los Estados Unidos, the curriculum covers topics about regions in Los Estados Unidos.
This indicates that U.S. history classes often include specific regional topics relevant to different parts of the country, while the other options suggest a lack of regional focus in history classes in either Mexico or Latin America, which does not accurately reflect the educational context in those regions.