No Stupid Questions

It does make sense though. The main motivator for politicians is power. That means, naturally political systems flow towards maximizing power for those in power, that's just the natural progression.

To change this, major political upheavals are necessary, so basically events where the whole old leadership is tossed out and the new leadership can try to setup something to stop the same thing from happening again.

WW2 was perfect for that. All those countries were in need of a completely new political system and thus they could be built better from the ground up.

The US never had any event like that (apart maybe from the civil war).

To change the system without such an event, two thirds of all relevant politicians would have to vote for changing the system that brought them to power. Not likely to happen.

Have you looked at the amendments? So far there have only been 27 of them over 236 years. Ten of them were created within a year of the constitution being created. They were basically Zero-Day-Patches, not actual amendments, and two amendments only exist to nullify each other (18 and 21) which leaves 15 amendments over 235 years (one of which was actually also created within the first year and only ratified 200 years later).

The last time an amendment was proposed was 54 years ago and the last one ratified was 33 years ago.

Not counting the Zero-Day-Patches, not a lot of these amendments actually change anything fundamental. Notable ones are 12 (governs the election of VP), 13-15 and 19 (civil rights), 17 (election of senators), 22 (president's term limit) and 25 (succession of the president).

Notably absent from the amendments is anything that changes the core political system or electoral system.

Compare that to other countries. In the time that the US constitution hat 15 minor amendments, France had a total of 15 complete constitution re-writes, not even counting amendments. 15 full new constitutions.

Germany had 69 constitutional amendments since 1949 (76 years, so almost one amendment per year, compared to the 1/16 amendments per year in the USA).

But by far the biggest issue is that a constitutional amendment cannot actually fix fundamental systemic issues. The people who have the power to change the constitution came to power within the current system, so if they fundamentally change how the system works (e.g. by repairing the electoral system in a way that more than two parties can be relevant), they are directly cutting into their own power, so of course they won't do that.

That's what you need major constitutional crises for (like e.g. Europe after WW2), so that the constitution can be re-written from scratch, fixing the issues that lead to the crisis.

But the US has been too big to fail for too long and thus there never was anything big enough to take down the US so that it needed to be restarted from scratch. The closest they came to was the civil war, but they didn't take the opportunity to actually overhaul the system. Probably because it was still too early and there wasn't much of a precedent of how to build a better democratic system.

But who knows, at the current rate it might be likely that the US is quite close to another chance to re-write the constitution.