Let's be serious here. I think it is safe to assume that nuclear war will never happen. It has no benefit for the aggressor, and thankfully, even the maddest leaders are intent on world domination and not destruction.
For me, the threat level of a country is based on the amount of misery they are likely to cause. Countries like North Korea are simply not threatening at all in this sense; they inflict misery in their own countries but they aren't invading others. Russia has a medium kind of score - the Ukraine isn't pleasant. ISIS scores pretty highly; with all it's new splinter groups, it is wreaking havoc on two continents. However nobody can compete with the USA. Scores of countries have been impacted by America's arrogant interventions for its own interests.
In the future, I doubt this will change. For change to happen, I think there needs to be more Vietnams. More serious failures in the USA's foreign policy. Only then will the public see sense. Half the population think the Democrats are too left wing; even though they themselves are right from the centre. There needs to be major liberalisation in the USA - the country is simply too extreme to not inflict pain on the world as it is.
Shut your bullshit mr UK us USers arnt arrogant u bloody idiot if we where arogant then why is every fucking immigrant in the world coming to the US instead of the UK ill tell u why its because the Brits are stuck up cunts that like to control everything