I know john Adams and Benjamin Franklin were among those who went to France, and later Denmark. There may not be a reason, but it seems odd I never hear about any Asian countries or peoples during this monumental time in American History.
Because Asia was very, very far away, and uninterested in meddling in European political issues. China in particular was famously isolationist during this period, and had very little contact with the West. You have to remember how relatively isolated the world was during this time period. Europeans and Americans knew almost nothing about Asia, and to ask such a unknown entity halfway across the globe for assistance would have been out of the question.
Furthermore, even if the Americans had asked China for help (wholely unlikely), they would have never complied. During this period, China more or less thought of all non-Chinese people as barbarians - people that could show up and pay tribute to the Emperor, but not equals that could be dealt with on an equal level. They cared very, very little about anything that occurred outside of China, and had almost no dealings with non-East Asian countries.
Off topic: this isolationist outlook and behavior continued more or less the same until the early-mid 1800s, when England showed up and started colonizing them in the opium wars. This was a huge shock to the Chinese psyche, as they quickly realized that they were outgunned by the European powers. In one of the most shocking events in Chinese history, Europe started the process of carving China up, and arguing over who gets what piece of China. For a nation that viewed itself as the pinnacle of civilization and power, this came as an absolute shock - in about one generation, they went from considering themselves to be the most powerful nation on earth to being carved up (and forced to purchase opium). This was a humiliating experience, and one that many Chinese have not forgotten.
Edit: I'm not sure if China had the means to send their armies to the eastern seaboard of the U.S. even if they had wanted to. They were not a great naval power, and to get there they would have had to go across the Pacific, around the tip of South America, and then up to Boston, or New York, or wherever. Not an easy journey.
Was any Asian country capable of helping the United States during the revolutionary war?