There was a lot of opposition to black people leaving the south because the white planter class did not want to lose their cheap labor if the blacks migrated westwards. They even went to the extent of closing the Mississippi River and intimidating to sink boats carrying the African Americans
1.) They had the French on their side.
2.) Guerilla Warfare.
Guerilla Warfare is a sort of petty type of combat - they ambush, use sneak attacks, etc.
Manufacturing, production and efficiency had increased through necessity during the Great War. America had emerged as a world industrial leader and the US economy was booming, profits were increasing which led to the period in American history called the Roaring Twenties with a massive rise in consumerism for the wealthy.
They were too large and expensive - typically a computer would fill a room and would have to have its own power supply.
