US mentality is weird. Most countries we understand that a “party” stands for certain principles, and so if you don’t like the party, you vote for a different one.

You’re apply logic and rules from completely different nation’s systems and calling the US’s version “weird” because it doesn’t match how other countries do it?

It makes no sense to demand that the party change to accommodate the voter, that’s not the role of a party.

Perhaps in your country it isn’t, but in the US, it is. During the convention of the party, the party chooses its “planks” for its platform. These are chosen within the party itself, and they absolutely change. You can see the 2024 Democratic party platform here if you want to. Here’s the 2020 version.. As you can see there are some large differences. The GOP used to do this same process before it was consumed by the cult of trump.

The role of a party is to try and change the minds of the population to support the principles of the party. A party exists to convince the masses to accommodate them, not for the masses to accommodate the party.

In your system perhaps. Not in the US system. It doesn’t make the US system “wrong”. Does it have shortcomings? Absolutely, all systems do. Are these various shortcomings equal to each other? That’s subjective. I personally would like more aspects of European-style politcal parties, but not everything that I see with parties there. We, as humanity, have yet to find the objectively “best” system.

What’s even weirder is the Americans who delude themselves into believing the Democrats hold principles they literally do not. They are very open about being a neoliberal nationalist party, but I have encountered weird Americans who tell me things like Democrats all support universal healthcare / “Medicare for All”

I’m losing faith in your arguments because you’re painting a picture that all members of a party share the same beliefs. Again, maybe that’s an ideal from your own country’s party system, but it isn’t in the USA. I would be surprised even in your own party if you have universal agreement on all policy positions.

There are individual Democrats that support Medicare for All. Here’s one example:

Hilary Clinton, as First Lady at the time, lead the creation of the Clinton Healthcare plan of 1993. This was absolutely a universal national healthcare plan:

“The task force was created in January 1993, but its own processes were somewhat controversial and drew litigation. Its goal was to come up with a comprehensive plan to provide universal health care for all Americans, which was to be a cornerstone of the administration’s first-term agenda.”

Does this mean that every Democrat believes in universal healthcare? Of course not. But to claim that none do, as you are, is equally untrue.

Even here on Lemmy, criticizing Democrats by pointing out how they are right-wing can get you downvotes from weirdo Americans who are convinced they are a truly left-wing party.

You’re going to have to be more specific with an example post, because most of the downvoted posts I see close to this are “both sides are the same!” garbage. Also, I don’t believe many believe the US Democratic Party is “truly left-wing” as would be defined in, lets say, Europe.