I am aware of the first-past-the-post system, but UK and Canada also have the same but their third parties gain national/federal seats.
In the US, it’s always either Democrats or Republicans. There are third parties on state and county level but never succeed on the national level. How come? Is the electoral college somehow impeding third parties?
Welcome. I’ve felt like that since 2000. I change my registration to match the challenging party for that election so I at least have a say in the primary. US citizens barely vote in the incumbent’s primary, so your vote may actually matter in the challenger’s primary.