As I see it, there are a some fundamental differences that make the Westminster parliamentary system more flexible and probably more effective (less ineffective?) than the US congressional system.
One is that there is a quick, painful way to resolve deadlocks: if the government can't get legislation though the parliament, it can call an immediate election. So, anyone causing a deadlock needs to do a calculation about their prospects at an election that might be called today for, say, six weeks time. Deadlocks for no good reason are rare.
Another is that the only mandate is for parliamentarians. The person signing legislation into law as the Head of State has no political mandate, so in practical terms bills that pass the parliament cannot be vetoed. They are signed into law on the advice of the government of the day.
Also, every office barer can be dismissed from their office (but not from the parliament) by someone else quickly. That tends to keep people on their toes too.
Further, any of those generalisations can be broken or varied or adapted to local preferences / conditions if it seems the right thing to do since the system is mostly governed by well entrenched 'conventions' rather than codified into rigid rules.
The ultimate arbiter of right and wrong is an immediate election.
