My short answer for the US joining is no. One of the reasons why I like Eurovision is that it's not US produced, and I can learn about great musicians from around the world. BBC America should show Eurovision with BBC commentators, because I bet they could find a target market for it if more people know what the show was. If you love our sets though, hire a US designer!
As for 50 Statesvision or whatever, we kind of already have that. It's America's Got Talent. I think due to cultural differences, the show is very different from Eurovision. For one, in stead of music acts people can perform whatever they want. Though most of the acts are musical. Additionally, there is not much of an age cut off. 10 year olds can compete against granny.
But what really makes AGT different from ESC is the attitude of the participants and the fans. Participators are trying to 'make it', therefore by taking themselves too seriously the show loses that funny and campy feel that ESC has, and makes ESC so wonderful. Also, I know people argue that ESC is not political, but it totally is. That is another reason why I love it, politics are fascinating! AGT is not political. And finally, the fans are such a huge part of what makes any show/ music act great. ESC fans are so passionate about the show, which is wonderful to see. AGT fans are no so die hard about it.
I can't see a ESC version of the show happening in the US. Then again, everyone in Hollywood also said 'The Voice' was the dumbest idea ever. So who knows.