The Littlefield collection is/was probably the finest in US private hands. My understanding is the original owner died recently, and the heirs have no interest in running the museum, so they've split it up and auctioned it off.

Nicholas Moran, who is the armor history expert for the World of Tanks video game, has made several videos about interesting vehicles in the collection on his YouTube channel (TheChieftainWoT). The amusing part is watching him trying to shoehorn his height into some of them. Especially the Soviet designs, since crew comfort was far down on their list of design priorities.