Robson saw off Taylor Townsend in the second round of qualifying before beating Ling Zhang to book her place at the Grand Slam event, which starts on Monday.
But Naomi Broady will not be joining her compatriot at the final Major of the year after the British number five fell in the third round to Stephanie Foretz Gacon of France.
Robson was made to wait overnight to meet Townsend after rain had forced the cancellation of several matches on Thursday, and once she took to the court, she was pushed all the way by the 15-year-old American.
The 17-year-old former Wimbledon junior champion had to fight back from 5-2 down in the third set to eventually prevail 6-3 4-6 7-6(0) and set up a second match of the day against Zhang of Hong Kong.
Robson, Britain's number four, found the going altogether less taxing as she closed out a 6-4 6-3 win to become the fourth British woman in the main draw, joining Elena Baltacha, Anne Keothavong and Heather Watson.
Broady had booked her place in the third round of qualifying with a 6-4 5-7 6-3 win over Chang Kai-chen from Chinese Taipei but met her match later in the day against seventh seeded Foretz Gacon, who ended the Stockport player's hopes with a 6-3 6-7(6) 6-3 victory.
Meanwhile, Irish duo Niland and Sorenson booked their places in the main men's draw of the US Open after sterling performances in qualifying.
Niland, who played in the first round of Wimbledon in June, will now get a chance to play at Flushing Meadows after completing his third victory at the qualifying tournament.
Despite losing the first set of his match this afternoon, the Limerick man kept his nerve to beat Dutch opponent Matwe Middelkoop in three sets; 2-6, 6-1, 6-4.
Earlier, Sorensen won his second round qualifying match against Gastao Elias of Portugal in straight sets.
Sorenson showed he wasn’t fazed by an opponent who was over 300 places above him in the world rankings after a 6-4, 6-1 victory.
That win sent Sorenson through to a deciding quarter against Martin Fischer of Austria, who is over 400 places ahead of him in the rankings, and the Irishman once-again flourished.
After winning the first set on a tie-break (6-2), Sorenson dropped just one game as he claimed the second to win the match 7-6, 6-1.
The two Irishmen will now have to wait for the weekend draw to learn who they will face in the first round at Flushing Meadows.