scenario 1: China China are in a territorial dispute with smaller countries over the South China Sea (despite it's name, the other countries have legitimate claims to it). if it gets out of hand, America may get involved. China and America go to war. Scenario 2: Russia Putin continues to attack Ukraine and doesn't stop until Eastern Europe is entirely under his command. massive fighting breaks out in Europe. Scenario 3: ISIS. with Iraqi forces always running away from ISIS, there's not much keeping them in check. they successfully take over the entire middle east. ISIS launches a major terror attack, akin to a second 9/11 (disclaimer: I DON'T WANT THIS TO HAPPEN). America then goes to war against a massive ISIS continent.