The Without a Trace star is back on home soil to promote the screen adaptation of gay activist Timothy Conigrave's memoir Holding The Man.
The book charts Conigrave's 15-year relationship with the captain of his high school's Australian rules team, John Caleo, who the author met when the pair attended an all-boys school in Melbourne during the 1970s.
LaPaglia, who plays the captain's father, Bob Caleo, says moves to legalise same-sex marriage in Australia have been a long time coming.
"If the United States beats Australia to making gay marriage legal, you're in trouble," he told AAP on Saturday.
"It says a lot about the current administration here."
A cross-party bill to legalise gay marriage is days away from being introduced to the federal parliament when it resumes on Tuesday following its winter recess.
Labor supports gay marriage but Prime Minister Tony Abbott has not granted his party a free vote on the issue.
"It just shocks me that we are culturally behind like that," LaPaglia said.
The government needs to take note of the growing support for same-sex marriage around the world, the Lantana actor says.
"Denying people their rights is like trying to fight your way against a rip tide."
The Emmy winner is hopeful Australia will move in the right direction not just on marriage equality but on issues concerning the environment and human rights.
"You hear a lot of s*** being thrown out against the US, but we need to look here," LaPaglia said.
"We should be a much more progressive country than we are."
He believes the love story in Holding the Man will touch many Australians.
"It will strike a chord with people who have an opinion on this issue, some negative, and it will turn some people's opinions."
