The event that got the USA seriously involved with WW2 was the attack on Pearl Harbor on December 7, 1941.
Louis XVI was executed during the French revolution.
Answer:
A divided regional identity (with a bit of national unity) developed.
Explanation:
Politics: Some contributed (voting rights) to unity, others (nullification) clearly divided the country.
Economics: Market revolution was a bit of both but Tariffs and the clash between the industrial north and the agricultural south was dividing the country and contributed to a regional identity.
Foreign Policy: The war of 1812 united the country; the westward expansion was uniting and dividing at the same time.
As we take in account that Economics is always the most important thing for the general public, the regional identity grew more than the national unity did.