What would the price be if bitcoin were used as the agent for clearing international trade?
I don't know how much space there is for bitcoin in that field. In large trades the two parties know each other and are backed by their respective countries, so they can rely on mutual trust (if one party defaults, that country's trade suffers) or trust in a third party (UN, WTC, International Court, US Navy, etc.). Also, much of that trade seems to be done on credit anyway. And volatility is going to be a big problem: one can forgive a 5% loss in a 20$ purchase, not so much in a 2 billion $ purchase.
We would have to wait for some examples of such use, before we can guess its potential growth. China importing 10 million frozen pizzas from Italy perhaps?