An evening at San Diego’s Snapdragon Stadium billed as a fantasy football encounter between a young Manchester United side and Wrexham was bad-tempered and aggressive, featuring a slew of yellow cards, one red, a serious injury to Paul Mullin, a half-naked pitch invader and victory for Phil Parkinson’s League Two team.

When Sam Dalby steered beyond Radek Vitek in the second half to make it 3-1 to Wrexham, substitute beat substitute – each had come on after the break – and the record 34,248 crowd had witnessed a contest in which United were run ragged for swathes.

Related: ‘Stay away from Wrexham’: club angry after Mullin injury against Manchester United

The game became combative 12 minutes in when United’s Nathan Bishop clattered Mullin, who never saw the goalkeeper coming and was left in a heap on the turf. The Wrexham forward required treatment that included receiving oxygen.

Seven minutes passed before Mullin, still breathing via the mask, was able to stagger off, and a night that began as the latest chapter in the fairytale story of Wrexham under their Hollywood A-lister owners, Rob McElhenney and Ryan Reynolds, curdled for Mullin, who reportedly suffered a punctured lung.

Bishop’s evening, too, took an unwanted turn. Having been shown a yellow card (the first of a total of four in the match), the 23-year-old was booed and jeers subsequently studded every touch of the ball of the former Southend keeper.

He and his defence would want to custard pie themselves due to how they allowed Wrexham to score their first two goals. First, Liam McAlinden’s delivery from the right was watched by a rearguard that included the rooted Bishop, and Elliot Lee ghosted in for a smash-and-grab opener.

The crowd adored the first goal – and they did the next one, too. It arrived again from route one approach play and again from Wrexham’s right: Will Fish was transfixed by the ball as it dipped in from Ben Tozer’s throw-in, Max Cleworth flicked on and Aaron Hayden, at close range, beat Bishop.

This was a test for Travis Binnion’s youngsters from United’s academy and a riposte from Wrexham to Mullin’s demise, after the feelgood ambience before kick-off in the Californian sun for this third fixture of the Welsh side’s first US summer tour.

Each of the Wrexham goals was met with a salvo of fireworks and United received the same treatment on the stroke of half-time, when the right-back, Marco Jurado, volleyed past Ben Foster.

Bearing witness to all this was McElhenney, resplendent in white slacks, white shoes, and a black and green print silk shirt. The American actor, along with Reynolds, has transformed the world’s third oldest club (founded in 1864) via the kind of magic that sport can supply.

Parkinson sent out an XI that beyond Foster, a former United and England No 1, featured Mullin, Tozer, Lee and other journeymen. Yet due to Welcome to Wrexham, the documentary screened by Disney and soon to have a second series, all have a level of fame Stateside; Mullin and Tozer have been recognised on a North Carolina street and San Diego beach.

The increased recognition has propelled Parkinson and his squad to a point where they found themselves listening to a rendition of The Star Spangled Banner while witnessing a fighter jet flyover as the anthem hit the climatic line of “O’er the Land of the Free and the Home of the Brave”.

None of this should be normal for a club formed in Wrexham’s Turf Hotel. Yet it is now because, as the unfortunate Mullin said in the buildup, “nothing surprises us”.

Against all of this United were a junior side apart from the veteran Johnny Evans, who was jittery despite a pedigree of three league titles claimed during his first, 11-year spell at the club. They were also a 10-man proposition less than two minutes into the second half after Dan Gore scythed down Andy Cannon and the referee, Mark Allatin, deemed it a sending-off offence. United’s captain on the night walked off in front of Erik ten Hag, the manager on a watching brief detail only before Thursday’s meeting with Real Madrid in Houston.

Emotion swept through the ranks of Binnion’s starlets as Álvaro Fernández joined Bishop in the book for another roughhouse challenge. Binnion could be pleased with how his academy products mixed it with seasoned professionals but less so if competitiveness became a loss of control.

From here tempers cooled and the invader ran on, swerving security momentarily before being wrestled to the ground. When the final whistle sounded Wrexham had given United a minor schooling and ended their jaunt to the States the best way.