Matterson, who only came in as coach on the eve of the tournament, has now led the side to two superb wins, with last night’s 32-20 triumph over the Cook Islands following on from a shock warm-up victory in France.
He said: “I’m over the moon. It’s nothing less than these guys deserve.
“They’ve come together, and I came in late, and they didn’t know each other.
“We had a good trial win in France, and then a great time together, and I am so proud of them.
“To do that out there today on the short preparation, and to come from behind a couple of times, I’m just over the moon for them.
“We’ve made another highlight tonight.
“I’m really pleased for USA rugby league. People like David Niu have put their heart and soul and money in to this for years and years and then a guy like Steve Johnson has come on board as well, and he’s been wodnerful. There’s a lot of people behind scenes, and these guys here, I’m just so proud of them.”
Matterson added: “We have three games in eight or nine days, and Wales are not going to make it easy.
“They have been resting for four days after their game, so we have to dust ourselves off and get ready.”