Why was the third party system disbanded?

Answer 1

In the US, there is no limitations on the number of political parties. With that said, much like the UK, it's difficult for a third party to gain much traction with voters. The US citizen relies on either the Republican or Democratic parties. In the UK, the voter, for the most part chooses between Labor or Conservative parties.

Answer 2

I am not sure what you want to know. The US never had a third party system. In 1824, before national parties became dominant, there were four strong regional parties. In 1860, the two major parties split geographically over the slavery issue and four candidates received electoral votes. In 1912, Theodore Roosevelt's new third party received more votes than the Republican President Taft. In other years a third party candidate would arise and attract enough votes to influence the election, but the third party came close to winning.