Finding something American to sell to the Chinese, whether democracy or widgets, has always been a problem. The first merchant vessel to sail from New York to Canton in 1784 was on a tea-buying voyage, but the cargo it had to exchange was ginseng. American ginseng was consumed by the Chinese for its yin: the female properties of cool, while the native product was thought more yang-heavy. A population explosion may have made it difficult for domestic production to keep up with demand, hence the opening for American ginseng merchants who made a nifty profit.
Thus was born a trading connection in which, for long stretches, the Chinese assumed they had the upper hand. They required silver in return for tea, without which, some believed, western barbarians would go blind and develop intestinal tumours.
As barbarians went, the Americans seemed a milder version of the British pest. It helped that British merchants initially shut Yankee competitors out of the opium trade, and that American missionaries inveighed against the evils of the drug traffic. So the image of the US benefited from being perceived as less vicious than the Brits.