I think the answer is the 10th Amendment
Sectionalism is the belief that a person's region was superior to other sections of the country. ... All of these issues led to sectionalism in the United States and pushed the country to the brink of war.
The USS Maine was sunk in the Harbour of Havana, Cuba, during a revolt of the cubans against Spain. Public opinion in the USA was that Spain was to blame. Starting as a diplomatic issue between Spain and USA, rapid escalation resulted in war between the two countries.
Led to the creation of a two chamber congress. Also created was the House of Representative which is determined by a state's population
