And he was pro-Germany, in much the same way that certain Americans today are pro-Castro or pro-Chavez. He was not alone in this -- the isolationist movement was politically quite influential.
What Lindbergh did, was to give them a famous face to put to their political position.
In many ways, America's isolationists were the other side of a coin bearing Neville Chamberlain's portrait.
A lot of commies were also in that camp once the Ribbentrop-Molotov pact was signed. Adolf then was the Commies' newest, bestest buddy.