List and explain examples of how the united states has dealt with foreign conflict

Going back from WWII is where I feel that the United States has had conflict with other foreign countries with the axis powers with Germany, Japan, and Italy. The U.S wanted to stay neutral to not get involved with the war until Japan bombed Pearl Harbor and had to pay back to them by bombing Hiroshima. But the modern day conflicts is that our allies is China but China is allies with North Korea which is our enemy. With China and North Korea having similar political ideologies, it gives a complex on China and U.S relationship. Our problems with North Korea now is that they're having nuclear tests and they're threatening to bomb South Korea.