I was thinking earlier this morning, what if the FCC tried something similar to what Canada is doing, and cull-out the smaller AM channels in the congested areas, allowing for AM's in the more widely-spaced areas to increase power on both daytime and nighttime service?
But that is not, in broad terms, what Canada has done. Canada has allowed the migration of many AMs to FM, in an "exchange" of the AM for the FM. In most cases, the AM signal has disappeared.
The exception is in larger metros with special interests, such as Asian communities in Vancouver, and the miltiethnic communities in Toronto: AM channels vacated by a a move to FM have sometimes been replaced with specialized services that serve these interests.
Several provinces, like Nova Scotia, PEI and New Brunswick are being left with no AMs at all.
Canada is not improving rural AM coverage or, in general, promoting the improvement of facilities by the remaining AMs. They are, simply, recognizing that AM reception in urban areas is plagued by interference and in rural areas the audience is better served by more FM relays and repeaters.
FM works fine when you are near a tower, but there are plenty of places "out in the country" where AM service improvements would be preferable.
But that is not what Canada has done. Among the first proponents of the move to FM was the CBC, which gave up its two clear channels in Toronto and the two in Montreal to move to FM due to the noise and coverage holes of AM.
Nearly any broadcaster who can has moved or is trying to move to FM under this policy.
In Mexico, of 759 AMs, 599 can tecnically move to FM and 506 have already received grants to move, and another 50 or so are still in the legal process of being licensed. That means that about 75% of all Mexican AMs will disappear, and not be replaced by any class of service.