The USD/MXN pair is neither a major nor a commodity pair, despite the fact that the trading volumes on it are relatively large. The USD is obviously a major (THE major would probably be a more accurate description), while the MXN is not.
The world’s most traded currency and the first one to go floating in the 70s, the USD is also the top reserve currency and the one in which some commodities (like gold and oil) are exclusively traded. Controlled by the Federal Reserve through the occasional tweaking of lending interest rates, the USD serves as the national currency of several other countries, officially or de-facto, and some 23 countries have their currencies pegged to it.
The strength of the USD is derived from the massive economy of the country, which excels in almost every regard. Commodities, energy, banking, services and manufacturing are all major sectors of the US economy.
The Mexican Peso might not be a major currency, but in Latin America, it is indeed the most traded. Its history is a bit jittery here and there: in its current form, it was introduced in 1993, after a government debt default. Since then though, steady economic growth and foreign investment in the Mexican economy have made the Peso remarkably stable.
By far the sturdiest sector of the economy of the country, services make up some 70% of Mexico’s GDP. Industry and agriculture play major roles as well.
Trade volumes between Mexico and the US are obviously massive. The economy of the former is the bigger beneficiary of this setup. Powered by the smaller economy, the MXN is usually the one presenting the trading opportunities on this forex pair.
Political turmoil in the country is obviously a major factor in this regard.