I'm in England and I infiltrate/damage in the USA across the border. Where am I tried? How is this confusing?.....
It isn't.................it is the internet, which does NOT have conventional boundaries and is not governed by international law. To imply that geographical boundaries delimit the internet is patently flawed.

For extradition to be in any way valid, the alleged activity must be illegal in the country in which it was initiated and would need to be tried and proven there.

The USA does NOT own the World and has no damn right trying to impose its laws on UK citizens resident in the UK. We have our own laws thank you very much.

Think about it folks, how many US journalists, authors and broadcasters have been extradited to China for criticising the regime there? It is illegal in China

The issue here is one of jurisdiction and extradition of YOUR OWN CITIZENS to be tried by a foreign court. Where they were actually resident in the country where they comitted the offence, the case is reasonably clear cut, except for religious and political "crimes".

Where there was a crime, it is where it was comitted that is important. The argument about shooting people across borders is spurious, it is an offence both sides, and it is the side where the gunman was positioned that is the determining factor.