Well I will tell you one thing that will get the US back up is military action by China.
And Japan might be weakened economically but it has not really stepped back militarily. If China starts lobbing stuff I surmise that Japan would step in (probably at the US request).
In all honesty, if China was smart they would just cool their heels for a while. The West is in the process of imploding so they only need to wait it out.
RE: China raises 14 grievances with Australia as $20 Billion is at stake