Meh, China is trying to reduce dependency on its exports and develop an internal market for its goods. The US economy is actually the probably only one economy that could survive without any trade - exactly what North Korea intended to do. I looked at the numbers comparing the size of total annual trade (import+export) with national GDP. For the US, the ratio is 25%, whereas it is 50% for China. The only other countries with a ratio <30% are poor third-world countries like Ethiopia and Pakistan that would probably do better with an export-driven economy.
If push comes to shove, the Chinese rely more on the US than vice versa in terms of trade. I don't know how debt comes into the picture but it obviously has an effect. If China attacks, it's probably not out of respect for the alliance, but in its self-interest for security purposes.