Chasing 218 for victory, Ireland were wobbling slightly at 105 for 4 after Ryan Corns dismissed Ben Ackland (16), and Lee Nelson (0) in the space of four balls.
Stirling however found the perfect partner in Graham McDonnell, and the pair settled the Irish nerves with a match winning 104 run stand in exactly 16 overs.
Stirling played very sedately by his powerhouse standards in the initial stages of his innings, content to take his singles, rotating the strike. He reached his half century from 63 balls, and that was the signal for the Middlesex signed batsman to launch an all out offensive on a beleaguered American attack.
He was particularly brutal on Naseer Jamali, striking him for 23 runs in total in one savage over, including a massive six over long-on to bring up a quite superb century, his second fifty coming from just 33 deliveries.
He was eventually dismissed for 114, a knock which contained12 fours and the aforementioned maximum. One shouldn’t underestimate the contribution of McDonnell (35*), who with 94 needed from 16 overs, took 14 from the 35th, launching the push for home with a huge six over his favourite midwicket region.
Earlier Ireland had lost skipper Andy Balbirnie for 3, while Stuart Thompson, dropped on two, played some lovely cover drives on his way to 27.
Ireland will be grateful they were only chasing 218, after it looked like a total of 250 would be their target.
However a late order collapse saw USA lose their last five wickets for just 17 runs, with Lee Nelson (3-3) doing most of the damage.
Saqib Saleem (62), Steven Taylor (57), Ryan Corns (31) and Gregory Sewdial (30) all batted well to take USA to a position of real strength before they imploded.
Taylor in particular dealt primarily in boundaries, striking 6 fours and 3 sixes as Ireland allowed him too much width to play his shots. Craig Young took 3 wickets, while Andy Balbirnie (1-26), George Dockrell (1-34), and Paul Stirling (1-37) all bowled containing spells.
The pivotal point in the game came with the run out of Corns by Lee Nelson – that saw just 49 runs added in the last 13 overs of the innings – which included a batting power play. As often happens in these situations, it conspired against the States, as they played a variety of poor strokes. Ireland weren’t complaining, and they
upped their game considerably in the closing stages.
Ireland now move on to Napier/Palmerston North later in the week, where they will face Zimbabwe in the first round of the Plate competition.