When the astros lost the World Series against Washington, Academy had containers full of shirts that were on the racks ready to sell - they were going to reopen the store just to sell World Series merchandise. When the astros lost the "reopening" didn't happen and the racks were cleared that night.
The poster above is correct most gets shipped to Africa and some gets shipped to places like Indonesia and the shirts are either destroyed, recycled into new shirts, or sold/given away dirt cheap in remote areas of the world.
This also happens with all those clothes recycling clothes bins in Walmart, target, church parking lots. Big money in this when the clothes are free or donated.
I do think like the poster above that the bills and Vikings have a huge following in remote/under the media radar of the world.
Here is a feel good article about some of this but don't be fooled as when you buy your shirt you are paying for cost of both.
https://www.mentalfloss.com/article/29884/what-happens-losing-teams-championship-shirts I collect ticket stubs! looking for a 1944 orange bowl and 1981 independence bowl ticket stub as well as Aggie vs tu stubs - 1926 and below, 1935-1937, 1939-1944, 1946-1948, 1950, 1953, 1956-1957, 1959, 1960, 1963-1966, 1969-1970, 1973, 1974, 1980, 1984, 1990, 2004, 2008, 2010