We see PMs easily enacting massive legislative reforms and even Constitutional changes that are nigh impossible in the US, that was not a particularly controversial statement.
I'm responding to this part separately because it's a very different issue. The existence of "superior law" in the form of a written constitution, is very silly. There need be only a single law, the law of the land - and the legislature must be able to change it - and only them, otherwise why have a legislature at all?
These are only man's laws, they're no different than the laws of Football ("soccer") for example, they are not facts about the world like Mother Nature's Laws - and so to hold some of these laws superior to others is a waste of everybody's time. The resulting paralysis in the US is not something to be praised, it's just another rusted joint, a lost degree of flexibility and so a point of weakness.
In reality, the supposed "impossible" constitutional changes in the US simply enable learned helplessness. Democratic representatives weep that alas much as they wish otherwise they "cannot" fix obvious problems because change is "impossible" and then of course somebody who actually does want to change things just does and says (as we might expect remembering these are only man's laws) if you don't like it too fucking bad.
The legislature can change the US Constitution. The federal Congress proposes an amendment with a 2/3rds yes-vote, then it must be ratified by legislatures of 3/4ths of the states.
The reason to make some laws harder to change than others is to protect civil rights. In the US, it is very difficult to legally infringe on the right to free speech, for example. In the UK, it is simply a matter of a majority vote in Parliament.
> Democratic representatives weep that alas much as they wish otherwise they "cannot" fix obvious problems because change is "impossible" and then of course somebody who actually does want to change things just does and says (as we might expect remembering these are only man's laws) if you don't like it too fucking bad.
Passing Constitutional amendments is perfectly feasible and has been done many times. It just can't be done without majority political support and the will to do so. They've been passed and "repealed" before, with Prohibition, for example.
A lot of kvetching in the US system (on both sides) comes from people whose ideas are simply not very popular and would like to change the rules so they win. In a democratic society, you need majorities of the population to agree. For larger changes, you preferable want larger majorities.
I don't know about UK but in Australia we need a Referendum (https://en.wikipedia.org/wiki/Referendums_in_Australia) to change the constitution and those have been historically extremely difficult to pass (only 8/45). The PM absolutely cannot alter the Constitution.
In contrast the Westminster Parliament routinely disposes of Prime Ministers who lose its confidence, it's already happened once in my lifetime and it's not some multi-week procedure in which there's some performance of a judicial process, just a simple question: Does this Government retain the Confidence of the House?
Margaret Thatcher decided on this course of action on a Monday, on Wednesday morning she rose to say, "Mr. Speaker, I beg to move, 'That this House has no confidence in Her Majesty's Government.'" and by the next morning the Callaghan minority government had fallen.
The problem wasn't the Crown, that's the big takeaway. Giving the same power to a guy who doesn't have a hat doesn't fix the problem. You need to hold this much power in commission, that's the lesson that gave us the present British arrangement - the Lord High Treasurer was much too powerful, so his power was given to a commission, today its First Lord though not nearly as powerful as the Lord Treasurer, is too powerful, that's the Prime Minister you gestured at - the formal office is "First Lord of the Treasury", with the Chancellor being Second Lord, and the whips taking subsidiary parts of the commission. If you ask me we should further re-divide this power.
But just giving all that power to one man (and in the US it has always been a man) is even worse. The US President has powers that a King had, which made sense in the 18th century but stands out today - that's why Trump can corruptly pardon people for example.
You seem fixated on the practical process of removing one from power, which is of course irrelevant as long as their party backs them, which is the actual threat in both cases. In either case, if the legislature does not back them, they can be removed from power with little issue.
I see in a sibling comment you think this is actually a weakness of the US system...apparently the PM radically changing all the laws, norms, and unwritten constitution of his country is "not powerful", while the US President typically fighting a battle to get one single major piece of legislation through in his career is unitarian dictatorship?
> , the US nation building projects stopped doing this themselves because it doesn't work, the United States itself is just a slower decay, it's not an exception.
The US nation building projects felt that parliamentary democracies were easier to control, as direct election of Presidential executives sometimes leads to democracies electing leaders who are able to carry out policies that violate US interests.