The Australians rolled Argentina in Mendoza 34-9 to move to the top of the competition ladder and set up a thrilling finale against New Zealand at Sydney's ANZ Stadium on August 8 with the winner to take the title.
The All Blacks, who over-ran the Springboks earlier in the day, would not be so easy.
"We weren't perfect by any means but we kept doing what we were doing and kept playing consistently over the match and pushing Argentina into making mistakes," Cheika said.
"It's very obvious that New Zealand are the best team in the world, and I mean by a long way at this stage.
"They've been so consistent over so many years, so just having a couple of wins in the Rugby Championship, you're not going to guarantee anything."
Cheika admitted the scoreline flattered his side after they only held a two-point lead at halftime, with two tries coming in the final minutes to secure a bonus point.
But he was delighted they showed patience to force Argentina into making errors and were able to grind out the win, which avenged their shock loss last year at the same venue under then-coach Ewen McKenzie.
Cheika said while his team may hold the ladder lead on points differential, it counted for little.
"We've done nothing," he said.
"We've played a couple of games, we snuck home in one, stuck at it in this one. We'll look at the next one when we get back to Sydney.
"We want to really try to keep improving so we can come into some shape over the next period before we go to the World Cup."
Making seven changes following their first-up win over South Africa, Cheika could again tinker with the side with back-rower Wycliff Palu and winger Henry Speight now available.
He was impressed with how Kurtley Beale sparked the attack when he came on in the second half, the difference prop Scott Sio made to the scrum, and also the work-rate of lock Will Skelton, who played his first full Test.
Replacement lock Dean Mumm was another standout, dragging three Pumas to the line for a crucial try in the 60th minute in his first Test in five years.
Flanker David Pocock was brutal at the breakdown, securing a number of turnovers in his first Test start since 2012.
"I thought he was excellent," Cheika said.
"He took a few opportunities on the ball and made a few runs so he's improved his ball carry this year immensely."
