The three-party system doesn’t work, proven by the 1992 election, where the right vote was split between “independent” Ross Perot and Republican George W. Bush. Since about half of the country had split into two different conservative candidates, the democratic candidate, President Bill Clinton won the election easily. This is why if the Libertarian party surges, the right vote will be split, and if the Green Party on the left surges, the left vote will be split.
Also, on a side note, a political party is not considered a “major party” until it has elected a president. Parties can also die and get replaced. For example, we started the two party system in the 1800 election between Federalist John Adams and Democratic-Republican Thomas Jefferson. Obviously, these two parties aren’t what we have today. Both parties sort of shared basic principles of both the Republican and Democrat ideas. In a way, the morphing of political parties is necessary because the country’s needs change. I hope this has helped you better understand why the three party system is not good for America.