The whole gov/system is by default 2 party system.
Some of the questions that you are asked during your citizenship interview is what are the two main parties.
Im not saying I like it. But it’s a fair assumption to make when literally all voters only consider the two parties.
[1] https://news.gallup.com/poll/15370/party-affiliation.aspx
You are given choices of “identifying” as Rep/Dem/Ind. Only two of them are real parties.
What does it mean to be independent then? Is it more like undecided?
Im not sure you can call that a political party.
I'm sure it means different things to different people. For me, it means that I don't follow any party's platform in lockstep. I try to judge each candidate and policy based on merits, not team affiliation and have voted for multiple parties over the years (Republican, Democratic, Libertarian, Green).