Coach Tony Smith said England must dramatically up their game after a hard-fought 32-22 victory over Papua New Guinea in Townsville.
England travel to Melbourne to take on world champions and overwhelming favourites Australia on 1 November.
"It's hard to dominate a rugby league match when you give your opponents so much ball," Smith told BBC Sport.
"We were rusty, we learnt some lessons but it was good to get a win even though we didn't play too well."
England had been expected to beat Papua New Guinea comfortably, but instead found themselves 12-16 down at half-time.
Buoyed by a sizeable contingent of supporters at the Dairy Farmers Stadium, the physical Kumuls outplayed their opponents in the first 40 minutes, with Hull KR's Stanley Gene pulling the strings at stand-off.
If we had won tonight there would have been three days public holidays in the country
Papua New Guinea's Stanley Gene
"People who doubted the opposition haven't done their homework," said Smith.
"They have got some very good players coming through, along with experienced players in Super League and the NRL.
"They are very enthusiastic with the ball, they are a very passionate team and playing nation.
"But credit to my boys, we knew we were a bit off and to improve the way they did in the second half, that was more of what England are about."
A hat-trick from debutant winger Lee Smith, along with two tries from Ade Gardner and one from Martin Gleeson, spared England's blushes.
The brilliant Gene said he was disappointed the Kumuls did not capitalise on their superb first-half performance.
"We were right there until the last 20 minutes," said the 34-year-old.
"No-one in this World Cup thought we would play like we did today, everyone wrote us off.
"But these guys believe in themselves and we showed a lot of people that PNG can compete with the best teams in the world. The country will be proud."
The result could have been that much closer had referee Shane Hayne not disallowed two Kumuls scores in the second half, the second a tight forward pass call on a David Moore touch down.
"We got two tries on the corner - one a forward pass and one where the referee thought I took the player out - we could have had 10 points," added Gene.
"They (the PNG population) would have liked us to win, if we had won tonight there have been three days public holidays in the country."
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