If US states are able to act independently, there is a greater chance for competition between jurisdictions, incentivizing states to provide a higher quality of life and to attract productive newcomers.
Lincoln thought the possibility of secession gave minorities too much power. The solution for him was for the majority to coerce the minority, negating, through force, the minority’s withdrawal of its consent.
The fascist form of interventionism in America was built on the rump of state corporatism that emerged during the Progressive Era and the experience of state planning during the First World War.