U.S. society and its politics are screwed up, but I'm not completely convinced it is due to the "U.S. system" (i.e. a congress and an independently elected president). I think any political system is prone to failure if the wrong people have political power.
For the past 4 years, the senate and Trump's cabinet have basically given Trump free reign to abuse political norms. But lets say he was the Prime Minister in a Canadian-style westminster system... Republicans would still probably retain an advantage (since they would appeal to rural ridings, which tend to have more political power). And because in the Westminster system, the executive branch has much stronger ties to the legislative branch, Trump would probably have even more authority to cram through laws than he has in the American system.
Two things he couldn't do are stack the courts...
While Canada does have various committees that review potential candidates, much of the authority still rests with the cabinet (who would would have been selected by, and likely subservient to, Trump)
From:
https://en.wikipedia.org/wiki/Judicial_appointments_in_Canada#Superior_and_federal_courtsThe Minister draws an appointment from the list of names received from the committees, and recommends that individual to the federal cabinet.So a Canadian version of Bill Barr would likely pick the most right-wing candidates selected by the commiittees. (And this is assuming that a theoretical Trump PM wouldn't change the rules to make sure only far right-wing candidates are examined by the committees.)
As for the supreme court: Also from Wikipedia:
Appointments to the Supreme Court of Canada...and are made on the basis of a recommendation to cabinet by the Prime Minister. Now, Trudeau did introduce another committee to deal with supreme court nominations, but there is no reason the procedure could not be changed to go back to a more direct nomination.
So yeah, in Canada the courts can be stacked.
...and compromise the electoral system.
Not sure how you define 'compromise the electoral system'.
Election methods and riding boundaries would be difficult for a Prime Minister to change, but he could (in theory) get parliament to change voter ID laws to suppress certain voting demographics (something he could not do in the United States, since those things are controlled at the state level).
It's interesting that when you look at any list of the best countries to live in, the top ten is dominated by constitutional monarchies with parliamentary systems. They also seem to be the most stable.
Yes, there are plenty of examples of stable parliamentary systems. But then, there are also some constitutional monarchies that have been less successful.
That countries like Canada, Britain, Sweden, etc. have been as successful as they have been probably has more to do with factors like levels of education, bigotry, etc.