I don’t believe China has any intention to support anyone by military means. Best case they will keep on trading and that’s it. Iran is alone. Maybe Turkey makes a crazy move to support seeing it sees itself as next in line if Iran falls. This is the biggest present to European powers, which I think will be hoping that it will keep US busy for rest of Trump’s presidency. They have the Ukraine excuse to distance themselves and let everyone get weaker while they arm themselves up. Internal political tensions in US will also give them leeway to more actively influence American politics and these will be even worse with a long war pitched against a scandal background. Then again, Trump may be a genius, get this done in a couple of months and leave everyone grasping for a new strategy.