US President Donald Trump took office as the "most powerful incoming president in living memory" and would win "if the presidential election were held again today", Australia's ambassador to Washington Joe Hockey has declared.

"Winning as an underdog leader gives you huge implied power," Mr Hockey said.

"In winning, Trump defied the pollsters, the critics, the media commentators and the Washington establishment ... no president before has been elected with so few political debts."

Mr Hockey, who delivered what he called a "report card" on the first year of the Trump presidency to the Lowy Institute in Sydney on Thursday night, said that while many in Australia and in the region had found the leader "unsettling", it's "worth remembering that President Trump was elected promising to shake things up".