The US political system is not other countries. How come people on this site are all about understanding systems except when that system stands in their way? How come so many people are experts on US politics and the political landscape therein without having studied it literally ever in their life? It’s honestly getting to be infuriating how little yall know and how far you think that knowledge seems to extend.
Even a glance at US history would show you that 3rd parties do not exist because when they do, one party collapses into a new 2 party system. Whigs, federalists, antifederalists are all parties that no longer exist. We had a 3 party system multiple times, but the issue is inherently that the system encourages 2 parties and no more.