1. One way sectionalism cause conflict in America was how it split the Northern and Southern states. The Northern states had different beliefs on slavery than the South, and they felt very strongly about them. Those different beliefs and loyalties are one of the main reasons the civil war started. Another way is how Northern states income mostly rested on it's different industries and manufacturing, while the Southern states income rested on free slave labor from it's plantations. If slavery became abolished, the South would have near nothing left to support their economy.
2. Sectionalism still affects politics today. The Western and Northern states usually tend to vote more Democratically due to their liberal nature, while the Southern states tend to support more Republicans.