To be honest, I think we need someone that's "too liberal" for America. The majority of why we elected Obama is we wanted change. Significant liberal change. We were tired of the eight years that we had under Bush, weren't happy enough with the establishment democrats, and wanted someone who would lead America by a leftist philosophy. After 6 years of Obama, we have yet to see this non-establishment liberal that Obama claimed to be. We have not seen most of the change that we wanted. Elizabeth Warren, so far as I can tell, would be the perfect choice to carry out the change that we wanted Obama to institute. She is not an establishment democrat, is a far leftist, and actually believes what she preaches. Our conservative counterparts might not like her very much, but if we actually want to become the #1 country, as we so often claim to be. We're going to need someone that is passionate about leading us where we must go. Elizabeth Warren is that person.
I'd say that most of what Obama has done has more or less been a tiny step forward, and a large step sideways. I'd say that we need to make faster progressive advancement. I mean, heck, look at the two parties that we have. The democrats, who are usually sane but fairly moderate, and the republicans, most of whom are complete lunatics that are stuck in the nineteenth century. Warren might be too liberal for the US, but she's more or less on par with liberals in anywhere else in the developed world.