England leapt ahead over the series leaders 14-0 after a clever feint in the second minute by Dan Norton, who a day earlier overtook Kenya’s Collins Injera as the Sevens’ all-time top try-scorer.
One more try followed a minute later from Phil Burgess before Eagles prop Ben Pinkleman capped a hat trick 90 seconds after the half-time break.
But captain Madison Hughes missed two crucial conversions and the Americans struggled to the 28-22 finish a man down when substitute Marcus Fasitupe was sent off after barely a minute onfield.
Wales snatched a 21-19 victory earlier in the day after riding out the clock following a 12th minute Joe Goodchild try and conversion by captain Luke Treharne.
“That Wales one was especially disappointing,” Hughes said after the England match.
“We just came out flat and not really with it. We’ve just got to have a hard look at ourselves… today is not the sort of day we want.”
The US will progress to tomorrow’s knockout round despite only one win in the group stage and start against South Africa, while England take on Samoa.
Reigning Hong Kong champions Fiji finished at the top of their bracket after a 24-5 demolition of New Zealand.
Buoyed by a vocal posse of blue-wigged supporters in the north stand, Livai Ikanikoda drove home Fiji’s third try a moment after converting for Vilimoni Botitu, bringing his side up 19-0 at the first half.
Joe Ravouvou salvaged some dignity for New Zealand in the closing minutes with his fifth try of the tournament.
Fiji and New Zealand have between them won two out of every three championships at Hong Kong since the tournament’s founding in 1976.
Australia finished third in their pool after their sole group stage 28-12 win over 2018 runners-up Kenya, who have struggled through the weekend with an ageing squad and in the shadow of a recent salary dispute.
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