That's a bizarre story, and it's the first time I ever heard of it. How the heck can someone launch an unmanned balloon and have it deliver explosives thousands of miles across the Pacific Ocean with any degree of accuracy at all?
That said, the Japanese weren't stupid and they figured out how to use the jet stream to send their balloon bombs across the Pacific.
As a side note, the Japanese were closer in 1945 to producing an atomic bomb than Nazi Germany ever was. This says a lot for Japanese scientific abilities.
From the late fall of 1944 through the early spring of 1945, the Japanese launched more than 9,000 of these "fusen bakudan", or fire balloons, of which 300 were found or observed in the US.
http://www.japan-101.com/history/fire_balloons_or_balloon_bombs.htm
Just because you never heard of it doesn't mean it didn't happen. And just because they weren't very accurate doesn't mean that they were a very real threat.
The US Government kept that the bombs were making it to the West Coast a top secret so the Japanese would assume they failed and give up on them. All the fires they started were kept out of the press (by a press that understood that if you leak military secrets people die).
You should really study World War II history before commenting on it.
Good gosh, you never heard of that?
" across the Pacific Ocean with any degree of accuracy at all?"
They had no intention of being accurrate, merely spewing terror and starting massive fires in forsts.
It would have worked, but a freak storm blew most of the balloons off course.
BTW, the balloons and the anthrax/plauge/cholera attack they had ready for the West Coast are completely seperate tactics.
And let us not forget what the Japanese did in Bataan.
(the Japanese had developed a simple bubonic plague bio weapon using aerial spreading of infected fleas...they tested them in China to nasty effect)
On the balloon bombs a decision was made at the time on our side never to report any so the Japanese would not know if they were reaching the North American mainland
There was also the were Japanese submarine aircraft carries(biggest sub in the world at that time, three attack bomber aircraft per sub)
http://www.subart.net/final_act.htm
They were intended to take out the Panama Canal locks... but could be use for other North American mainland targets
The Japanese has some other advanced weapon in the work at the end of interest... See
http://www.j-aircraft.org/xplanes/index.html