several things could've happened 1)The people who live in Texas would be sworn enemies with Californians and Floridan would hate Maine people and so on.
2)Our lives would be different as we know it
3) The outcome of all future wars(WWI and WWII) would have many differences.
4)there would've probably been a second civil war
try reading harry turtledove's How Few Remain. Its about an alternate history if the south had won the civil war