I don't think the U.S. has an analog. Thatcher was iconic and spawned strong reactions politically as well as in popular culture in a way that no politician in the U.S. has. The last public figure that I can think of who influenced music sales upon their death was Michael Jackson.
Correct me if I'm wrong, I'm not very well read in this area, but it seemed like Reagan and Thatcher had some very similar views. While perhaps Reagan was sort of a George Bush figurehead who had his minions do most of the dirty work, he was nonetheless a figurehead of some extremely damaging and regressive controversial shifts in policy. When he died, there was none of this celebration, but an outpouring of sympathy. I found the UK's reaction to her death kind of odd. It seemed as though Reagan and her were viewed in a similar light by similar groups of different societies.
I think there's something to that, but I think for a lot of people in America, Reagan though significant, did not have the same iconic stature that Thatcher did for many in the UK. Why this is, I don't know. I wasn't even in kindergarten when the Reagan administration ended.
Any time an artist dies, their music sells like crazy. For example, Whitney Houston "had a nearly 60-fold increase in album sales" after her death.