there are still things the USA needs to import and failing that they can always export capital in the form of loans
Coffee, tea, opium, and tropical wood all come to mind as US imports in game. Possibly many manufactured goods, depending on how many artisans, capitalists, and factories they start out with.
And being an exporter only works if people can afford to buy your products. No WM to soak up all of the US exports this time. I hope there is a quick and easy way to see what % of your output is being bought, per industry.
Finally, as con rises, so does consumption, so US POPs will consume more of their local goods and import more as well.
I'm curious, I know that people with the highest prestige buy first, but do people buy from highest prestige nations first as well?