The main problems that caused the changes in the political parties were the disagreement between the North and the South over slavery, Industrialization, and immigration.
American Party - also called Know-Nothing Party - and Whig Party were strongly against immigration and wanted to end it.
The Free Soil Party was created to fight against the rise of slavery in the new territories won from Mexico.
After the Kansas-Nebraska act people were unhappy with the compromise, because of that Free Soilers, Whigs and Democrats came together and created a new party called Republican Party.
The Democrats were divided between North and South Democrats, Southern Democrats wanted to continue slavery, Northern Democrats were against it. Because of that they divided the party and created the Constitutional Union Movement.