How has the world since 1945 been bound together more tightly but also more contentiously?

1945 was the around the time period when the second world was came to an end, the world did not want another out break and so the United Nations have tried their best to maintain world peace, that is how they are bound more tightly , after the many years that have passed, it is possible that war can occur at any moment and so nations are always on guard making their relationships contentious