Again, a lot of people don't understand how sanctions work.
The US is not stopping the money flow, the US is stopping the people that want to deal with Iran of conducting business.
If someone wants to deal with Iran, they are free to do it, if a bank wants to deal with Iran they can do wire transfers for Iranian companies, the problem is that once they do that they can kiss goodbye to any other business in the western world.
That's why China keeps on buying oil and sells the stuff because they do it through companies that have no other business relations in other countries.
Just because you pay something secretly with bitcoin doesn't mean that they will want to deal with you in the first place, they could have paid in gold, oil silver or sheep, their problem is that nobody wants to sell or buy stuff from them as long as the sanctions are in place.