In the instance of China, the greatest damage would be lose of the one thing most holding the economy together - and that is the reputation of the American dollar and stability of the American economy. That would vanish, and so would our economy.
Otherwise, within weeks every retailer in the USA would be closing for lack of inventory. There are not idle USA factories to just turn back on. Already suffering, those retailers would quickly go defunct and defaulting on their business loans - plus the massive layoffs those would cause - and the other residual unemployment that followed.
T-note sales would go flat, causing a rapid increase in interest rates, just as there would be a rapid increasing in inflation, shattering people's savings and retirement funds. The radical increases in inflation, unemployment and interest rates would devastate the housing and real estate markets, shattering the banking and financial industries.
Oil would go off the dollar standard, another permanent devastating consequence to the value of the dollar.
China, of course, would seize all American assets in China, such as the 15 GM factories built with bailout money (13 USA auto factories closed) and GM all but instantly back in bankruptcy - since GM now sells more vehicles in China than the USA.
The stockmarket would crash.
Overall, the result would not be a depressive, but massive inflation where money became all but worthless.
China is manufacturing self sufficient. The USA is manufacturing dependent. China would be harmed, but China being a totalitarian society familiar with hardship would survive. The USA would be shattered and still another effect would be the country going radically to the left and socialism as people tried to use government to get a piece of the radically shrinking pie. Investment money would flee the USA.
Declaring we would not honor debts to China as a winning strategy is unbelievably naïve.