I want to compare and contrast the US and UK shows. Some things might be considered spoilery, but I doubt at this point that they're following very much where the UK show went, although Paul Abbott is listed as a consulting producer or something in the credits.
Mickey and Ian never got together in the UK series, except in a throwaway scene in the epilogue of one episode. In the US, they're a major couple.
Karen is gone from the US show. She was a major character throughout all the seasons of the UK series.
Sheila is still in the show, but she didn't have the twins, Kev and Vee did. She is probably the character who diverged most from the original series, although she started out the same.
Kev and Vee are still in the US show and have children, and aren't in prison in Romania for baby-napping.
There is no Lillian in the US series. She was a madam who ran a brothel in the Chatsworth on the UK series. Mickey is running this instead in the upstairs of the pub.