SomeOne Wrote
why is it that shortwave
can actually go so far yet AM and FM barely go anywhere?

FM is in the VHF band thus is essentially line of sight (like TV Stations)

AM stations have a coverage during the day that is local - a few hundred
miles example I am in San Diego and can pick up LA stations 90 miles away.
At night one of the atmosphere layers dissipates and AM stations can be
heard all across the country. Example on a good night during the winter I
can pick up WGN Chicago - 1700 miles

For AM you will need a good antenna and listen at night during the winter
months.

All this is explained (no math) at URL:
http://ecjones.org/propag.html

CL