Ended the party--in the War of 1812, the northern Federalists lost trade with Great Britain.
Federalists believed the US must become an industrial country not a farming country. The Hartford Convention was a discussion of New England states leaving the Union. When the war ended, they no longer needed to leave because they could trade with Great Britain again and the country now were united in creating an industrial country with a national banking system. The Federalist party disappears and the US is a one party country until the 1828 election.
There were actually four HUGE causes for WW1, treaties and alliances brought many countries into war, the imperialism of some countries scared other countries, and they were "defending" themselves, there was a lot of weapons stocking, and countries were creating gigantic armies, and that threatened other countries, and then we have plain old nationalism.
