The six-year-old prodigy from Five Oak Green was competing against 111 other children in his age category in the three-day competition at the Pinehurst course.
More than 1,600 young golfers were taking part overall in the flagship junior event, which has been the subject of a documentary on Netflix called The Short Game.
Alexander shot a round of two under par on the first day, which put him in second place despite fierce competition which saw the US leader shooting seven under.
On the second day the Capel Primary School pupil was again on top form, retaining the runners-up berth with a round of one under.
Amid intense humidity on day three, he was unable to recover from a bad hole and dropped back to eighth place, but he was still the highest-placed European in his age group.
His mother Claire said: “We thought maybe he would make the top 20 but we never dreamt it would be the top 10.”
A place in the top 20 means he has automatically qualified for next year’s Worlds, and he will also be competing in the US Kids European Championships after coming third at Longniddry in June.