[seabass-labrax]

The article you link to is about radio navigation based on ground stations. The USA would have required at least an island near the Japanese mainland on which to establish such a ground station, or perhaps a ship if it could maintain an accurate position based on traditional methods.

Even then, I don't think it would be correct to say that the Americans had no other capabilities for targeted attacks. With air superiority you can do strafing at relatively low risk, which is very accurate. And the USA had also developed rockets by this point, which could drastically improve accuracy when compared to unpropelled bombs. They even used these operationally against Japan before the atomic bomb attacks.