No Stupid Questions

Not really.

In some countries, they have this idea of Defensive Democracy which would allow the government (via court ruling) to ban political parties that are deemed to be a threat to democracy.

In post WW2 Germany, the nazi party was banned, and later a "far-left" (aka: Marxist-Leninist) political party was banned during the cold war, because they meet Germany's definition of being anti-democratic.

Unfortunately, the US constitution does not have this concept of Defensive Democracy.

I mean we do have impeachment... but we all know how that is (doesn't work at all).

100 years? We very nearly reached 250.

The mechanism was the election.

I mean, sure, impeachment and whatnot, but it's not like people didn't know who this guy was. I can give other institutions a whole bunch of crap for not getting rid of the guy the first time, but when you've given him a Supreme Court supermajority, both chambers of Congress and the presidency AFTER he attempted a coup I'm gonna say that's on you, guys.

this is why giving too much power to a single position within gov is not a great idea

We’re ignoring the constitution already.

14th Amendment. Section 3. No person shall be a Senator or Representative in Congress, or elector of President and Vice President, or hold any office, civil or military, under the United States, or under any state, who, having previously taken an oath, as a member of Congress, or as an officer of the United States, or as a member of any state legislature, or as an executive or judicial officer of any state, to support the Constitution of the United States, shall have engaged in insurrection or rebellion against the same, or given aid or comfort to the enemies thereof. But Congress may by a vote of two-thirds of each House, remove such disability.

The man is an adjudicated insurrectionist. Congress just ignored their duty.

So yes, there “are” protections. Said protections are simply being ignored.

Not that it would be used, but the 25th Amendment is another avenue to removal of a President.

Is 53 out of 100 senate seats really enough to make country fall into authoritarian regime?

Well you'd need 60; 53 is enough to do a lot but you can't amend the constitution or override filibusters.

Is the army really not constitutionally obliged to step in and save the day?

Usually when the army "saves the day" by removing a democratically elected president undemocratically we call that a military coup and it's considered, to put it lightly, a bad thing.

America isn't at all volatile as a democracy; as you surmised, it's on the robust side (sans nonsense like citizens united). However, there's not much that can be done when the anti-democracy guys won democratically not just the presidency, but also all government posts that would be able to stop them.

The USA has had a literal Nazi party since the 50's. If they let George Lincoln Rockwell run for president while calling himself a nazi why would they do anything?

I believe this is where the second amendment comes into play. Luigi was on to something.

Let's just say the amendments are sorted by importance.

There are a few tools in the constitution.

Impeachment, but that starts with a 218 vote in the House and the House is on his side.

But who will wield these instruments? It'd be more relevant if he made an effort to hide his nature before the election.

Right now the majority voted fascism with open eyes.

The mechanism is impeachment. It's broken because of polarization.

Really because the rest of us have been watching you be wildly volatile for years now.