May boosted his chances of making the England XV for the tournament’s curtain-raiser against Fiji on 18 September by scoring the opening try in their 21-13 victory against the Six Nations champions on Saturday.
The 25-year-old had a further try ruled out following a forward pass from hooker Tom Youngs, while fellow winger Anthony Watson also dotted down.
“It was crucial to get the win,” said May. “We came out all guns blazing and with real intent. We haven’t treated these matches like warm-up games, every one has felt like a one-off international.
“If we were going into the World Cup on the back of two losses, it wouldn’t be a good place to be.”
Gloucester’s May has endured a turbulent international career but has emerged as a potent attacking force for head coach Stuart Lancaster after being axed during England’s Six Nations campaign earlier this year.
“I feel I’ve done all I can do. I’m happy with the way I’m playing at the moment and I’m still learning and improving,” added May.
“These warm-up matches have given me an opportunity to put things right after getting dropped in the Six Nations and to show the improvements I’ve made and confidence I’ve gained.
“I’ve been very hard on myself, scrutinising and reflecting to see what I can improve on. That’s a relentless desire to get better regardless of the circumstances.”
Wales full-back Leigh Halfpenny, meanwhile, will have a scan today on the knee he injured during his side’s 23-19 win over Italy. The injury places Halfpenny’s World Cup participation in doubt, as does the ankle problem sustained by scrum-half Rhys Webb.
England face Pool A rivals Wales at Twickenham on 26 September.