England, the world number one side, are heavy favourites to defend the inaugural title they won last year in New Zealand.
Head coach Mitchell used the game to rotate his squad after comfortable victories in WXV1 warm-up matches against France and world champions New Zealand.
It was a slow and error-filled start from both sides, before a clever line-out move led to Atkin-Davies scoring in the corner.
Mitchell decided to rest captain Marlie Packer and star wing Abby Dow for the opener, leaving it to Kildunne – another one of his regular top performers – to produce the required magic.
The full-back took the ball in her own half and weaved around a number of defenders, showing a clean pair of heels to finish.
But anything Kildunne can do, Kelter can do better. The United States centre regathered her own chip kick and stepped around a number of Red Roses to quickly respond.
After all that magic, Kelter then gifted England a third try, dropping the ball for flanker Brock to pounce for a first Test try, which was followed by a sharp finish from Matthews.
Ranked eighth in the world, the USA suffered heavy defeats by New Zealand and Canada in this year’s Pacific Four Series and showed lessons had been learned from the loses, remaining competitive to score twice in the second half.
Debutant Westcombe-Evans remained a threat throughout the game and despite being touted for her attacking ability impressed also in defence.
Fly-half Zoe Harrison, who started the Rugby World Cup final defeat by the Black Ferns in 2022, was brought in to start only her second game for the Red Roses since recovering from an anterior cruciate ligament injury. She kicked effortlessly from the tee – missing only one conversion.
Since her injury, England have struggled from the kicking tee, which may put pressure on regular starting fly-half Holly Aitchison, who struggled at times during the Six Nations.
Tougher tests are to come against the Black Ferns and hosts Canada, when Mitchell will likely bring back his main starters.