A fifth defeat in seven tests and the first at home to the Pumas in 35 years, sent twice former World Cup winners Australia tumbling to seventh in the world rankings, an unprecedented low.
"I just have an overwhelming feeling of having let people down," the 30-year-old said in a column on the Rugby Australia website of the 23-19 defeat at Robina Stadium.
"We were outplayed and at certain parts of that game we were out-enthused, and people will say: 'Hold on, how can that happen when you're playing for your country?'
"And it's a great question, because it shouldn't. That should never happen when you are out there playing for Australia."
Pulling on the green and gold for Australia made Genia feel like a "Superman", he added, and while the players were putting in the "blood, sweat and tears" on the training ground, he understood fan frustration at the inconsistency on the pitch.
"As Aussies, you want to see guys have a go. That's what it is all about right? Guys having a genuine go," he wrote.
"Playing with intensity, heart, determination and courage and having that never say die attitude.
"If we show those traits in our games, then we can lose and live with it. But if we show those traits in our games, we won't be dropping many.
"That's why losing on the weekend was probably the hardest loss I have ever had."
FAN FIGHT
Genia said Michael Cheika was preparing the side better than any coach he had ever worked with, but the players were losing their clarity and focus when under pressure on the pitch.
Australia departed from Sydney airport on Saturday to play their final two Rugby Championship tests on the road in South Africa and Argentina without forward Lukhan Tui.
Tui, who had played the game just days after the death of his stepfather, had an altercation with a fan in the stands after the Pumas loss, an incident Genia described as an "unfortunate episode".
"I am assuming the guy after the game had too many beers, and he has gone way overboard in how he responded to the loss," he wrote.
"(But) more than anything, to me it just showed how passionate he is about rugby in Australia.
"People who come out and watch us play, and show that much love and passion for the Australian rugby team, we want to make them all proud.
"We have an opportunity to go do that in South Africa and Argentina. We are in a tough place, and we have to respond. We will respond."
(Compiled by Nick Mulvenney; Editing by John O'Brien)
