I'm still scratching my head over the Spanish music there, though. David would know this for sure, but all I can imagine is habit formed of non-political motivations -- like if there are countries south of the border where AM listening is still prolific, and from which immigrants cling to AM upon moving here
The only country in all Latin America where AM is still significantly strong is Argentina, but that nation is really the southernmost nation in Europe. And all the high rated AMs are hugely powerful: 50 to 100 kw in Buenos Aires and 10 kw and over elsewhere. Because of the turbulent politics in that nation going back about 80 years, there are 5 or 6 talk stations with very big numbers.
Elsewhere, AM is disappearing. In Quito, Ecuador there were 40 AM stations when I put my first on one the air in 1964. Now, there are about 12 that are still on the air regularly, and half of those are cultural or religious. San Salvador had about 30 AM stations, and now there are around 10, all either government or religious.
Mexico's legislative body declared that AM was dead and proceeded to allow for lesser second adjacent channel FM separation so that about 80% of existing AMs could move to FM. In a couple of Mexican states, all the existing AMs moved to FM (some AM channels were relicensed, particularly to cultural groups or to rural locations where one of the hundred or so indigenous languages and dialects is spoken).
Even Cuba has moved most listening to FM, but they keep the nearly 200 AMs on the air to block foreign stations from being heard.
. But even that idea falls flat, as unlike for the Asian community, there are ample Spanish stations on FM here.
While the Hispanic Spanish dominant audience in each market is generally of one single region with a similar dialect, Asians come from many nations, each with one or more languages. That makes it hard to build a big enough audience to justify a full FM signal. Still, when one group is concentrated in a smaller area, we see Class A FMs serving them, such as the Vietnamese language station in Santa Ana, CA.