Here is the thing...
I am not really sure "the system" is to blame. I think any political system is prone to corruption if the wrong people get involved.
Canada has been pretty stable, and while I may not have voted for Trudeau or Chretien, I never got the impression that they were actively trying to destroy the country. Could you imagine someone like Trump as a Prime Minister, where there would be even fewer checks and balances to his power?
I agree. The US system has checks and balances. Trump can't introduce legislation, he depends on 2 different houses of Congress. Then there's the SCOTUS, and term limits.
In Canada, if there's a majority gov the PM can serve unlimited terms where he/she can introduce and vote on bills and whip members of his party on how to vote, and chooses the members of cabinet, the members of SCOTUS (as they are replaced), the GG, and the Senate (as they are replaced). Those are his checks on power.
Luckily the provinces need to consent to changes to the constitution.