The young Magpies got off to a flying start at the One Call Stadium, courtesy of Cathal Heffernan's early opener, before goals in each half from Max Dickov and Finn Flanagan turned the contest in the League One side's favour, who fielded three full internationals.
Newcastle's second-string, however, sent the Northern Group F clash to a penalty shoot-out in the dying stages following Ollie Taylor's stoppage-time own goal, turning the ball into the net from McArthur's cross-cum shot, before the visitors gained a bonus point via penalty heroics after successful conversions from Sean Neave, Sam Alabi, Joe Brayson and Seung-soo Park, with Dom Dwyer's blazed effort resulting in McArthur dispatching the winning spot-kick.
The Scottish defender, who has represented his country at under-21 level, told newcastleunited.com: "I think we deserved it. In the second-half, we came into the game and showed the kind of team we are. We were playing well, especially against a good side in League One, backed ourselves from the start and ended up getting a decent result.
"Going one-nil up settled the nerves and helped us to build from there. We stuck in for the first-half and we did well to go into the break level and we played well in the second-half.
"The boys dug deep. We conceded from a silly set play, which we could have done better with, but we showed the character to come back and showed the quality we have in the team."
Newcastle's late fightback keeps their hopes of progressing into the EFL Trophy knockout stages for the first time since 2018/19 on course and, should Huddersfield Town fail to beat Mansfield in their respective Northern Group F fixture, require a victory after 90 minutes against table toppers Harrogate Town.
McArthur, who made his senior debut for hometown club Kilmarnock at the age of 16 in October 2021, was delighted to contribute positively in the shoot-out and is relishing the test against Harrogate, who currently sit in 17th place of League Two, in their final group game.
"The boys back ourselves on penalties," the 20-year-old added. "We stuck to what we've been practicing in training and managed to walk away with an extra point. It was a good feeling to score the winning penalty. It's always good to score a goal, especially a penalty.
"Whichever team you play, the mentality is always trying to win. Harrogate will be a tough game but we back ourselves to do that."