You can claim all you like that the US is a multi-party system, but everybody can see that that is not how it works.
It very literally, factually, is. There are quite literally at least 50 different political parties in the United States. And a very simple Google search will reveal that to be the case. I very literally named a handful of them. Two minor parties always get about a half a percentage of the vote in presidential elections, with the Libertarian Party that has 700,000 registered voters, and 650,000 votes at the last presidential election. The Green Party with 261,000 registered voters, and 813,000 votes in the last presidential election. The Constitution Party came in 3rd place of the minors, with 155,000 registered, and 54,000 voters.
These are enough voters for these parties to prevent either of the major candidates from obtaining 50% of the vote. It would mathematically be impossible for one candidate to have 47%, and the other to have 46% if other parties and their candidates were not present.
Again, it is just a simple matter of states passing a ranked-choice ballot. A lot of major cities have it, such as NYC, and LA (that amounts to about 20 million in population right there alone!) And with the entire states of Maine, Alaska, and Hawaii for state-wide elections.
The three minor parties I mention in this post are pretty healthy. Especially the Libertarian and Green Parties. They've gained a lot of new traction, since people in three entire states and many large cities can actually now vote for them in local and state elections without detracting from "their side" in those elections. In the three states mentioned; Maine, Alaska, and Hawaii, they can vote like that in state-wide elections. This gives a crap load of people.... literally millions of voters....more incentive to vote for one of the minor party candidates in presidential elections.
The next step is for states to start instituting the rank-choice for presidential ballots. And it probably is not too far off, as younger progressives like Mamdani in NYC, are moving up the ranks of the Democratic Party. If Mamdani can become governor of NY in the 2030s, and if NYC voters heavily vote in favor of progressive candidates to their state chamber, then there's a really good chance that NY could join Maine, Alaska, and Hawaii to pass ranked-choice for state-wide elections and possibly move onto doing so for presidential ballots.