That seems incorrect, you can be prosecuted in your country of origin just fine for stealing from or hacking foreigners
https://www.zdnet.com/article/new-nigerian-law-means-seven-y...
There are countless examples of state sponsored hacking. There's no way the actor would be punished in the country of origin if their country of origin was not only OK with their actions but supporting them. Does that mean whoever did it should be free to travel anywhere they want without repercussions? You're essentially saying that countries are no longer allowed to enforce their laws on any foreign citizens... that seems EXTREMELY short sighted.
Furthermore, how would the country of origin even prosecute when the victim wasn't one of their citizens. What are the mental gymnastics to say that your citizens can't be prosecuted anywhere but their country of origin...b ut the victims have to what? Travel to your country to get justice? If a nigerian scammer is caught, you expect a US citizen to fly to nigeria on their own dime to try make their case?
Countries are sovereign, a Nigerian person living in Nigeria is only beholden to laws of Nigeria.
In your world, you can accuse someone who lives in Mongolia of a crime that doesn't even exist is Mongolian legal system, such as some peculiarities of US copyright or packaging of lobsters. You seem to think they should be flown to the US to be tried at your convenience to in a language they don't speak, in a legal system they don't understand at their expense?
You could prosecute him in Australia for hacking in whatever form it broke Australian law. How can any non-US citizen be held responsible for some vague 'damage to US national security' if they have nothing to do with the US? Why should a hypothetical person living in Nigeria be responsible for US, UK, Russian, Saudi, Israeli and everyone else's national security?
An individual can't 'make war', only countries can do that.
We are talking about an allegation (not proven!) of a crime, highly political in nature to boot, not 'retaliation'
But you couldn't prosecute Assange in the UK for conspiracy to steal documents from the US and damage done to US national security, but at best for damage done to UK national security through that.
(It's possible I am misunderstanding something?)