There was a fear of invasion of the mainland United States among members of the public. When the Japanese invaded Kiska and Attu in the Aleutians some congressmen from the Pacific Northwest claimed there was a threat those islands would be used as staging bases for an attack into the United States. Militarily this was absurd, Kiska & Attu were strategically worthless and Japan was no more capable of invading the United States than they were of landing a man on the moon. The concern about their use as a springboard was real enough though that it led to political pressure on the US military and to the mostly pointless effort to recapture the islands in 1943.

Edit: My sources for this are Pacific Crucible and The Conquering Tide, both by Ian Toll.