Here are some more:
The consciousness of humanity is rising : The current people of the world is the most aware lot in the entire human history. 40% of the world has internet access, 85% has Television. People today have more wisdom and understanding of what’s going around, they have become visionaries and are able to see the bigger picture. They are mindful of the dangers of World war III and will never let it happen.
The current world is run by capitalists : Decisions that our governments make are largely influenced by the capitalists through lobbying. Billionaires make donations to political parties to fight elections and the politicians return the favor when they come to power. A World War would have a tremendously disruptive effect on the economy and render the capitalists with losses. So, they would sway the govt policies that could lead to World War.
Cold War : The Cold war taught the world that a war doesn't have to be conventional or one on one. It can be fought in a third country by supporting an insurgency or by helping the Govt of that country withstand the insurgency. Since this has become the new warfare, there is a lesser chance of direct confrontation of the powerful nations.