This is a non-issue. Trials are held in the place where the crime was committed and where the victim had the loss. That is standard criminal procedure the world over, and extradition treaties are set up to recognize this fact and allow accused criminals to be returned to the location of the crime so that they may stand trial.
This whole thread is nothing more than a transparent attempt by some people to push a political agenda(s).
As for McKinnon, my opinion on him is that same as anyone else accused of a crime: Let him stand trial. If he's acquitted, then he can go home to the UK. If he's convicted, he can be thrown in a US jail like any other felon who's committed a crime against the US.