No, that's completely unrelated. In that case, the alleged crime took place in Sweden, so the Swedish courts are attempting to prosecute him. London's involvement is merely that countries have international extradition agreements, to prevent all criminals from being able to avoid the law by moving country. The US' involvement in purely speculation - maybe they're pulling the strings, but they're not officially involved.

So unless you think all extradition should be avoided (and whatever you think about the Assange case, would you be happy if somebody who lived near you murdered your family, moved to a neighboring country and you were told "well we can't do anything any more"?), the case has been handled perfectly from the point of view of which countries should do what.

But usually crime must be crime in both countries for extradition. The problem is that it is not required for extradition between member states of EU in case of rape, but definition of rape is still very different between countries.