England went into the finals on the back of a six-match winless streak and relegation from the Nations League.
But they put in a fine display to beat Iran 6-2 in their opening Group B game, Bukayo Saka scoring a brace and goals from Jude Bellingham, Raheem Sterling, Marcus Rashford and Jack Grealish giving Gareth Southgate's side a fine start.
Sitting deeper in midfield, Rice also had a great World Cup debut and said the questions over the squad and manager Southgate were ones the players were keen to emphatically answer.
"It was a positive start," he said.
"There were a lot of doubts about us before the tournament. There has been a lot of talk about us not winning in our last six matches.
"By our standards, with the players we have got, we know that it hasn't been good enough. But this was a World Cup stage and you could see there was a fire in our bellies.
"We wanted to prove a lot of people wrong. People will say, 'It's only Iran' but they have had some good results at past World Cups.
"In September, they beat Uruguay and drew with Senegal. It was a real positive performance but we can't get too ahead of ourselves. It's the USA next and they are going to be another level up."
Rice enjoyed a fine midfield partnership with Kalvin Phillips on the run to the Euro 2020 final last summer.
But it is Bellingham, 19, with whom Rice - four years his senior - is now developing a relationship and the West Ham captain knows his role in the coupling.
"We have played together four or five times now," he said.
"I said to him in the tunnel, 'This is your stage, go and flourish. I'll be there behind you to sweep up and give you the ball for you to go and do your thing'.
"I know my role in this team. I am there to stand in front of the back four, protect, get on the ball and move it around.
"I feel like we did that really well (against Iran). We stuck to the game-plan and in the end the spaces opened up. You saw the goals we scored with some real lovely play.
"You know you are starting to grow into it and the confidence comes from there. I knew I was going to play in my first World Cup.
"You don't get that feeling so often. You play in the Premier League every week but this is the world stage.
"It's something you never dream of and then you are here. We don't want to get too ahead of ourselves. There is still a long, long way to go and we will stay level-
headed. First game, first win. We can't ask for any more."