Fa'asuamaleaui said the anthems before Samoa's semi-final brought him to tears.
He had considered representing Samoa to honour his late father's heritage, but chose Australia again.
He also faced Brian To'o during Samoa's Siva Tau, when their heads made contact.
Australia's 44-12 semi-final victory set up Sunday's World Cup final against New Zealand.
The final renews a contest from last month's opener, which Australia won 24-22.
New Zealand controlled territory and gained more metres through its forwards, but three long-range tries helped Australia prevail.
"You win the battle, you win the whole game," Fa'asuamaleaui said.
Trent Robinson said on Seven Network coverage that Australia had been out-muscled by New Zealand and Fiji.
Luke Keary warned the pack could be steamrolled by Samoa or Tonga after Australia's 36-22 group-stage win over Fiji.
New Zealand's pack, arguably the world's best, includes James Fisher-Harris, Moses Leota, Joe Tapine and Naufahu Whyte.
"A lot of people probably have disrespected us, probably overshadowed the fact that we did win," Fa'asuamaleaui said.
He said Australia accepted tough scrutiny but considered some comments disrespectful, noting the Kangaroos have won the most World Cups.