While I agree that medical marijuana has a place in our medical society, I believe that each country should be responsible for growing and maintaining our own sources. There are not many places in the world that the plant doesn't grow, so it wouldn't be unreasonable to give farms an incentive to grow for medical production.
The United States should definitely trade (import and export) in marijuana for medical purposes. Marijuana is already legal in the US in several states, and even more if you include legal for medicinal use. It is only a matter of time before it is completely legal in the USA and by trading in it, the US can increase their economy.
Importing and exporting goods is good for all the country's economies involved. I don't think we should place a stigma on medical marijuana, and should import and export it to the other countries to help our economy. We can also try to lessen the fear of growing the crop, since it is still illegal in some states to grow it.
No, I do not think the United States should export and import marijuana for medical purposes because drug cartels will have the ability to directly impact our economy because a once illegal substance would now be legal. Although exporting and importing marijuana would help bring more revenue to the United States, I don't think the United States should get involved in the business.