Last week, player Rob Hawkins said England “were not playing to our standards” in their opening 98-18 win over Wales and rated the team five out of 10.
Asked how he would rate England’s showing against the USA, Billington told Premier Sports: “At least a seven. All week, we have been banging on about playing the way we want to play, and the boys really stuck to their principles.
“I’m over the moon for the guys to put on such senior performances.”
Finlay O’Neill was named player of the match as he recorded 38 points, with two tries and 15 conversions.
“It was a good team effort, not just myself,” O’Neill said. “We talked about how we could improve, and I think we did that.
“We need to take the positives – [there are a] few areas to work on but I think we can be very happy with that performance.”
The four semi-finalists have now been set, with the final group games to decide who faces who in the knockouts.
In Pool A, Ireland ensured they will qualify alongside England with a 68-28 victory over Wales.
Ireland, who are ranked third in the world, will face the English in their final group game on Friday in Wollongong (06:00 GMT).
In Pool A, two-time champions France and hosts Australia both booked their passages through while scoring triple figures.
France, who were losing finalists against England in 2022, thrashed New Zealand 120-10.
Australia beat Scotland 104-24, and will play the French on Friday to determine the pool winners.
Scotland, New Zealand, Wales and USA all go into a ranking competition to determine fifth through to eighth place.
Wales will face USA in Pool A on Friday, while Scotland play New Zealand.