I'm not sure what is "Americana" and what is "Alt country", but I listen to a lot of this stuff.
The Flatlanders, Steve Earle, Lucinda Williams, The Bottle Rockets, Uncle Tupelo, Bill Malonee and the Vigilantes of Love, pretty much anything on Bloodshot Records. There is tons of this stuff. I've also been into old hippie country weirdness like The Flying Burrito Brothers.
I don't know if anyone out there has XM, but I have been lucky to do sound for Robbie Fulks Secret Country radio show at the Old Town School many times. He has many new country as well as lesser known classic country guys on the show, does an interview segment, then each of the two artists featured do a set. Fulks himself is an awesome anti-Nashville musician.
-d