It want be like CIV I North vs South. More like total chaos in every state. Rural vs City or taxpayers vs freeloaders.
Mexico will make their invasion from the south official. Canada will sit it out probably with borders closed.
Whoever can control the supplies like Food and Arms wins.
What they win not sure of.
310million American will probably drop to 100millon or less. Most will probably die of starvation or disease not hostile actions.
:)