well it won't just be the US who will be fighting db? the US has a lot of enemies (N.Korea, Russia, Iran, etc.), that is given. But until this enemies of them present themselves in battle AS ONE, the US and its allies can just pick them off one by one. This guys have a lot of pride and think themselves mightier than the other so a unified enemy front wouldn't be feasible in the next 100 years at least. they have too much ego and their ideology is different. I can see Russia, China and N. Korea help each other but that's just about it. And think about the S.China sea. Its an important shipping lane. What do you think will happen if the shipments are harrassed by the Chinese Navy? What if they suddenly impose tax or fees when they pass through this channels?
Look at it this way. If you're a private businessman, will you invest in a place where security is in question? The Chinese are claiming international waters. Its supposed to be open to everybody. But since the Chinese are building military infrastructures around this areas, shipping lanes are threatened. Kung businessman ako, bakit ko padadaanin ung delivery trucks ko kung san may nakabantay na NPA o Abu Sayyaf? Destroying an economy ain't gonna happen overnight too. It takes a lot of circumstances to pile up to actually feel that your economy is getting weaker by the day. That is where the advantage of the Americans hold. America's economy is mostly reliant in creating wars. Mas nagging active ang economy nila kung my gera.
At kung magkagera ang China at US and its allies, which economy do you think will suffer the most? The ones being attacked or the one who's attacking? Who will help China during this time? Russia? N.Korea? Russia is being watched by the EU and NATO. N. Korea can be dealt with by S. Korea. Iran? They're being surrounded by countries that are mostly allied with the US. And they have ISIS to deal with. China doesn't even have the technological superiority to match the US. They're building "UNSINKABLE AIRCRAFT CARRIERS" kuno sa S.China sea. ang kaso, that is also their weakness. Its not mobile. A few passes of F-18 raptors can flatten this bases. And they have to deal with Japan on the east. China also has strained relationships with India on the right side. This is not an economic war.