CL is definitely not a flop in the US.
I would say she is doing good but not great. It's not like shes "the next big thing" but she is seeing decent success. Her English songs received mixed to positive reviews from fans and critics alike. She does have a following here and has connections to people in the US entertainment and fashion industries. Yes I am sure that some of the people who attended her concerts just like Kpop and wanted to be involved. But most of the people there went because they love 2ne1 and love CL.
CL has done things that have rubbed me the wrong way too. But nothing so bad that she is now a bad person.
For me personally, the only thing she has flopped with is her claiming she wants to be this big role model for Asian women. But when I see videos like Hello Bitches and the lyrics of Lifted, I don't really believe her.
As someone who is in America, I would say that CL is doing well for a foreign artist. The worst case scenario is that her debut album does okay and only maintains her current fanbase and does not garner mainstream success.