@Mushroom
I laughed at people a few years ago who cheered when the last President passed some things by Executive Order, and said they could never be undone.
THen I laughed again at their screams as the current one undid a lot of them. And it was not the Orders or their being struck that I laughed at, it was the stupidity at the idea that any President could really do something that would become permanent.
An action taken by any President or Congress is only as strong as the people's will to obey it. Absent that, it falls. And if this forced against what the people want, a representative democratic republic ceases to exist and instead turns into a despotic dictatorship, i.e. the rule of man supplanting the rule of law.
This mistaken principle, that what any one President ordains, another can't put asunder (sound familiar?) has been around for awhile. But it will remain correct unless forcefully challenged. Which, as you pointed out, is what happened.
Political actions follow a certain hierarchy of strength in the U.S. (don't know what it's like in Europe). Weakest is Executive Orders, followed by passed laws (signed by the President), followed by treaties (only if approved in the Senate per the constitutional process), followed by Constitutional amendment.
But, as you point out, all of these can be overturned. By another Executive Order, revocation of the law, abrogation of the treaty, overturning of the constitutional amendments (happened twice in U.S. history).
Most people are amazingly stupid at what the Government can and can not do.
That was what the proponents of permanence of one President's diktat were relying on.