All other channels are Regional channels.

If the expanded band is regional (these are local, I thought...) then there is
52.


Expanded band stations are Class B, for now, although I wouldn't put it past
some country to try to notify one of theirs as a Class A.


Again, the 60 clears are total for North & South America, or am I mistaken?


Total for this ITU region.


There is at least one Class I station (either Class I-A
or Class I-B) on every clear channel, and all such
clears are clearly identified in the NARBA and Rio
treaties as to power and antenna efficiency (although
for some Mexicans, the antenna efficiency may be
bogus).

Where would this listing be located on the web?


The FCC AM site.

List all stations on any clear channel (by specifying no call letters and
restricting the frequency range to any one specific clear channel) and observe
the class letter.

"A" is Class A, "B" is Class B, etcetera.

On a clear channel, you should find only As, Bs and Ds.

Central American stations will show up, too, and some of these are notified as
described, but many are not.

My assumption is if the FCC database has no class letter, then the United
States has not "accepted" the station's notification, or the class is
indeterminate.

It is common for any change to be submitted to Canada and Mexico for
acceptance, particularly in border areas, and vice versa.

This is one reason why almost all of L.A.'s FM's are operating way above Part
73 power ... because they started out that way, and when it came time to
formalize those existing operations, Mexico was requested to accept those
operations, which Mexico did, thereby "grandfathering" those stations with very
high (most) or even super power (KPFK).