You can even make a case that almost nobody should be extradited to the US by any country, since the US justice system has serious flaws, might not be just at all (e.g. it has about 10 times longer maximum prison sentences than in the rest of the civilized world) and the US penal system constitutes a constant human rights violation. For example, the administrations of many US prisons are notoriously unable to prevent the raping and murdering of their inmates. I've even heard people from the US making jokes about prison rape, as if that was to be expected and part of the "justice". As another example, a prison in Illinois was under 23 years of permanent lockdown, meaning that all inmates were in isolation for 23 years. There are credible accounts that Assange is facing imprisonment in high-security isolation facilities similar to what they did to Manning for a long time. I cannot understand why any civilized person would allow a treatment as inhumane as in US maximum security prisons with isolation, regardless of the crime.
Generally speaking, countries should review their extradition treaties. US justice is non-proportionality based on revenge and involves frequent human rights abuses. The same is true of other countries like Japan or Russia, but AFAIK extradition requests to these countries are much rarer.