Particularly given his obvious willingness to betray an ally, Russia. I doubt he considered the cost, things were going pretty well at the time. Enemies have often mistaken the essentially peaceful personna of America for lack of courage and will.
Hitler was known to play cowboys and Indians as a child. He admired America for what they did to the native American Indian, taking away their land the way they did. Not surprising from someone who made no secret of Germany’s need for Lebensraum, plans to usurp lands to the east to expand the Third Reich’s living space.
Haven’t you read The Plot Against America? Hitler was expecting Lindbergh to get elected President and become his ally and when that didn’t happen... no, wait, wait, that was just a novel...