The United States changed significantly after the War of 1812. One big change is that we had only one political party for a period of time. Towards the end of the war, the Federalist Party was viewed as selfish and unpatriotic because they were against the War of 1812. After the War of 1812 ended, the Federalist Party disappeared. Only the Democratic-Republican Party existed after the War of 1812 as we entered the Era of Good Feelings.
The power of the federal government grew after the War of 1812. The court case of McCulloch v Maryland stated that a loose view of the Constitution was legal. The case of Gibbons v Ogden stated the federal government controls interstate trade. The American System developed. This allowed for protective tariffs, having a national bank, and improving and building our roads and canals.
After the War of 1812, our industries began to grow. More factories were built, and people moved to or settled in the cities to work in them. Protective tariffs gave our industries a chance to compete against the more established and more efficient European businesses.
There were many changes in the United States after the War of 1812.