I touched on how the War of 1812 hurt the Federalist party [here] (https://www.reddit.com/r/AskHistorians/comments/13tcp5/the_war_of_1812_and_its_impacts_on_the/) which briefly touches on what happened to the Republicans. I also have a post on the fall of the Whigs somewhere that I will see if I can find

These explanations will be semi-simplified: The Federalists collapsed in 1815 during the Hartford Convention. The Federalist Party had been waning ever since Washington died and the disaster that was known as the Adams administration. The Hartford Convention was very much against the War of 1812 and specifically collapsed after the Battle of New Orleans made everybody feel awesome (hence the Era of Good Feelings). The Democratic-Republicans basically outgrew themselves after becoming the prominent party in America during the Era of Good Feelings, climaxing in the election of 1824 when there were 4 Republican candidates. This is when Jackson split with his own party, the Democrats, which have evolved their political views for each era of American history (which is why they have been so successful for so long). The Whigs virtually collapsed as well by 1854 due to infighting over slavery. From the remnants of the Whigs came the Republican Party, which took over in 1860 with Lincoln. Ever since then it's been the two party system.