If company X in country Y wants to trade with the US, they could require that country Y provides full transparency in carbon emissions, where the measurements from space could be used as a checksum.
Neat tech. (For those curious, it seems like we are capable to measure CO2 increase or decrease to an uncertainty of approximately 0.3% [of CO2, meaning ~1ppm overall]. That's impressive.)
Even if the last "embargo uncooperative countries" strategy were possible, I think you'd find that all of their domestic production would be carbon-intensive and their exports would all be "carbon neutral".
Well, we could require that countries (trade partners) pay tax on their emissions as opposed to companies. How these countries tax their companies internally could be an internal affair entirely. And this also solves the bookkeeping at the border.
Even if the last "embargo uncooperative countries" strategy were possible, I think you'd find that all of their domestic production would be carbon-intensive and their exports would all be "carbon neutral".