Lawsuits in China are not lawsuits in the USA. You could win but very doubtful. Avalon has no US presence so you would have to do it entirely in China. Right or wrong it's not gonna happen.
There are two questions involved.
- whether you can sue in New York, given the seller is in China.
You might be aware of New York long arm statute. The idea is that if there is any connection with New York (with some exceptions), then you can sue in New York. In this case, although the physical presence is China (what we assume), but the bitcoin address (as well as the valuable coins) are indeed online anywhere. You cannot say the bitcoins are located in China only. Some orders are even made from New York. So there is a possibility the court in New York will be willing to hear the case (jurisdiction issue).
- whether you can enforce in China if judgement is made in US.
It is difficult if you got a US court judgement and try to enforce in China. However, you can try arbitration. There is something called New York Arbitration Convention. The idea is that if you receive an award from arbitration in US and seek monetary enforcement in China, then the Chinese court needs to honor (with some exceptions).
Indeed, in the case of bitcoin dispute, given that the valuable bitcoins are not located only in China, it is on the worldwide internet and recorded by so many individual computers, it is likely, if technical savvy, to seize the coins without going to China physically.
*Disclaimer - the information is intended to be general legal information; it is not legal advice. Specific legal advice can only be given with full knowledge of all of the facts and circumstances of your situation. You should seek consultation with an attorney familiar with the laws of your state.