I'm currently watching "Chulas Fronteras y del Mero corazon" a great documentary without a narrator. Very impressive and under appreciated film. It Chronicles lives of Mexican Americans, and mexicans while only playing Mexican music. Great film.
You may be interested in this earlier answer of mine, where I talk about the European influences on northern Mexican and Texan music genres like the norteño. German and Czech Polka (through strong migration from those regions) were especially important which heavily feature the accordion.
Just to note though that Mexico is a huge country with very diverse musical traditions featuring lots of cool instruments. Those you mention, while probably better-known in the US than others, come mostly from northern Mexican regions with historically much exchange to southern US states. So those would also be more visible for Mexican Americans esp. living on those parts of the US. I'll be sure to look into the film you mention, sounds great.
Mexico is similar to places like India which have multi-cultures and cuisines within it's borders. Accordion music is popular in the North but there are many other types of music throughout the country that are not Accordion based.