I dunno, their success in the US started declining by the early 80s and then eventually the US lost interest in them, while they were still really big and whatnot in other countries. Also the fact that they pretty much stopped touring the US by then. That was also a big part of 'losing the US'. Also, the follow up to The Game (their most successful album in America and worlwide I think) was Hot Space (lol)... so yeah.
They were really popular in the US during the late 70s and very early 80s. For example Crazy Little Thing Called Love ('79) hit number one in America before they even finished The Game album. Also, Another One Bites The Dust was on the charts for quite a long time, on the number one spot too. Black stations picked it up thinking they were a black band and played the hell out of it.
Basically, playing in America in the 70s they eventually build up some success in there, hit the peak of it by 1979-1980 with Crazy Little Thing Called Love and Another One Bites The Dust from The Game album, followed it up with Hot Space, didn't really tour America, and by the time The Works album and the I Want To Break Free video came out, America kinda lost interest. Then after that, they didn't tour America and that was pretty much it with their success there. All though they're still really big all over the world, not really in America though.
But yeah, like MJJLatvia said, watch Days Of Our Lives. You'll have a way better understanding of all of this.
From 39:08 to 1:22:52 .... watching the whole documentary would also help with the understanding of other topics and whatnot, but if your interested in the whole America thing, watch that part and you'll understand everything much better. Much better than I could explain, especially since I didn't really mention a couple of other key things and various details.