The Secret Balloons that Bombed America

During WWII, Japan launched Project Fugo, sending fire balloons across the Pacific to attack the US. These balloons, made of washi paper and carrying incendiary devices, were largely ineffective, with only one fatal incident in Oregon. The US government covered up the attacks to prevent panic. Despite the project's end, unexploded bombs may still exist, with one found in Canada as recently as 2014.

How did the Japanese military's approach to warfare change after the initial months of Project Fugo?

Why did the U.S. government choose to cover up the news related to the Fugo balloon bombs?