From the article: “Total foreign imports are only about 11% of American consumption, and Chinese imports are 3%. Most of any national economy, including ours, is domestic; you can't import a haircut, a house, or a hospital visit. So global trade is probably overblown as an issue generally. Which isn't good news; it's just to say that, as usual, most of our problems are our own.”

You seem to have forgotten the core expenditures of a household: Shelter, Food, Personal Care and Entertainment.

Very little in there is coming from China. Certainly not food and most likely basic goods like stationery, toys, electronics, furniture and clothes. Seems reasonable to think that chinese goods fit the 3% figure based on the expenditure in those categories.