The Red Devils failed to win any silverware in the campaign and recorded their lowest finish since the formation of the Premier League as they placed seventh in the top flight.
Welbeck notched just nine goals in 25 appearances for United, but he is looking to capture his best form for the Three Lions.
He told reporters: "We have just got to put the season behind us and focus on the World Cup and try to do our best for the country.
"It is good to go and participate in a World Cup, you dream of it as a kid and one of the bonuses is that it is in Brazil and I grew up watching them in World Cups as well as England.
"It is an exciting place to go and we are looking forward to it."
Welbeck has scored eight goals in 21 caps for England.