Apart from command of the military and Supreme Court nominations, the US President has very little power. A hostile House can almost completely negate their political influence.
A parliamentary leader like the Australian Prime Minister has a much greater control of the country. By definition, they command the support of the parliamentary majority, and any MP who openly opposes the PM will be instantly expelled from the party.
OTOH, a PM who loses the support of the majority of their party will no longer be PM, even if the next election is years away.
What the US President has is too much prestige. Y’all tend to act as if they’re divinely-appointed kings.
(and before the “but you have a Queen” response gets posted: yes, we do. She’s seen as an irrelevant and rightfully powerless bit of archaic decoration)
