Yes compared to the Euros it was minimal. The old They did it Too? It seems the Moral Police here have different yardsticks for the 2 Sections. Guess it was Legal, oops, no it wasn’t. Yankee Merchants participated in the Opium Trade and the new Slave Trade from China to Cuba and Peru during this period.Then in reference to the Yangtze river squadron they apparently did so with the approval of Southerners the shape of Jeff Davis. Are you suggesting corruption in politics? Now we all know that could never happen with southern gentry involved.
US involvement in China was minimal when compared to the Brits or French. As China had a Civil War that made ours look like a common bar brawl at roughly the same time as ours... I don't think the linked article is quite so knowledgeable as you might like to think.