Dan Norton's hat-trick of tries saw England overtake the USA to clinch a 31-21 win in their opening game at the London Sevens.
England - chasing New Zealand for a first-ever Sevens World Series title - were trailing midway through the second half at Twickenham Stadium.
But Bristol Rugby wing Norton touched down three times in the final four minutes to make sure his side sidestepped a shock setback with captain Ben Gollings and forward Tom Powell supplying the first-half tries, and Gollings adding three conversions.
England were due to face Pool B rivals France and Argentina later today with the group winners likely to meet New Zealand, Kenya or Wales in tomorrow's quarter finals.
Head Coach Ben Ryan's side went into their home event trailing New Zealand by 13 points in the overall table and realistically needing a London tournament win to keep their title hopes alive going to Murrayfield next weekend.
But they were severely tested in their opening game despite surging into an early 14-0 lead against the USA.
Full-time sevens players Gollings and Powell scored their early tries - one in each corner - with Gollings supplying both conversions.
But they missed the chance to put a couple of other scores away and the USA responded with three tries around half-time, Matt Hawkins, Paul Emerick and Shalom Suniula all touching down with Suniula converting.
Norton's first two tries edged them 24-21 in front, though, and his third, from the final play of the game, put them out of sight.
In the earlier games Scotland came close to pulling an upset before being edged out 19-15 by Samoa and Wales eased through 33-10 against Spain.
Series leaders New Zealand eased through 28-12 against Kenya, defending London champions Australia beat Canada 19-14 and Portugal came closest to pulling off a shock until Fiji claimed a late try to salvage a 24-21 win.