At the time Japan had lost nearly all of the land gained during their conquest, and the U.S. clearly had the upper hand. So my question is, would a blockade of Japan have been feasible?
We did set up a blockade towards the end of the war, by dropping sea mines around all Japanese ports. Google "Operation Starvation." As to whether it would have led to surrender easier or more bloodlessly than the bombings or an invasion — it is not easy to say.