Assange should receive a fair trial in an American court. It may be a little more difficult depending on the type of trial. Jury trials are always more difficult in situations like these. Regardless of peoples perceptions of a person, one should always be able to attain a fair trial in this country.
The controversy that has surrounded court rulings and jury decisions for decades proves one thing: Americans are both willing and able to think for themselves. Assange's worst stains (Swedish allocations of rape and sexual assault) would not be the focus of his trial in an American court. Therefore his argument for innocence/acquittal could rest heavily (if not solely) on the idealism of transparency and free speech that Americans love oh so much.
I know he has said he would come back to the US, but I don't buy it. The man has been so careful to avoid extradition and has made no effort to solve his problems and come back and face his consequences. What makes us think he will now? What makes us think we can believe his word? I say we need to wait and see, as I just don't think he'll follow through.
The American justice system is not renown around the world for being fair and unbiased. Powerful people in the US will try and do everything they can to imprison Assange. Assange has many enemies and the US has the most to loose with Wikileaks publications.He will not receive a fair trail by any means.