Geraghty, the London Irish fly-half, and a number of other rising stars will use the tournament to stake a claim for inclusion in Brian Ashton's World Cup squad in September.
"If the Saxons can impress in this tournament then there's no reason why a few of the boys cannot be named in the World Cup squad," said Geraghty, who has shaken off a hamstring injury.
"Brian spoke to me before the squad for South Africa was announced and told me that I wasn't going to be considered.
"He said that playing in the Churchill Cup was a good opportunity to get my fitness back and play a few games."
Geraghty made a stunning senior debut in the rousing 28-16 Six Nations win against France at Twickenham in March.
He added: "I wanted to go to South Africa but when you take a step back, you realise it's probably best that it will be more beneficial to get more game-time under my belt, rather than go to South Africa and not play much.
"But hopefully I can use playing for the Saxons as opportunity to prove what I can do, and it would be fantastic to then go to the World Cup."
Besides Geraghty, attention will also be focused on how Ryan Lamb, the Gloucester outside-half, recovers from the disappointment of his team's heavy defeat to Leicester in last weekend's Guinness Premiership final.
The six-team Churchill Cup pitches the USA, Canada and guest side New Zealand Maori against the second string from established rugby nations England, Ireland and Scotland.
The Saxons will face a USA side made up largely of US-based college players, for whom it will be ideal preparation for the World Cup in September when they come up against defending champions England and southern hemisphere giants South Africa.
Nigel Melville, who was appointed chief executive of US Rugby last October, said: "Playing against England, and the likes of Shane Geraghty, is going to be a huge ask for our boys but we'll be able to see what the gap is between ourselves and them.
"It's about getting used to playing at their pace and trying to bridge that gap.
"Above all, it's an outstanding opportunity to play against some very good players and see what international rugby is all about ahead of the World Cup."