Houston - The United States stunned Scotland 30-29 on Saturday, rallying from a 15-point first-half deficit to record their first win in history over the world No 6 side.
"We made it scrappy and defended like hell," said US captain Blaine Scully. "We might not have the cap count but we know how hard we are going to work for each other."
The 15th-ranked Americans, who are now coached by former Sharks boss Gary Gold, fell behind 24-13 at the break but stormed back to take a 30-24 lead when AJ MacGinty converted after flank Hanco Germishuys scored a try halfway through the second half.
Scotland's Dougie Fife then scored a try in time added on, cutting the US lead to just one.
But on the final play of the match Blair Kinghorn's conversion attempt sailed wide, handing the USA a shocking victory and their first win over Scotland in five official Tests.
"The character we demonstrated to battle through adversity in the first half and for us to stay within our game plan is something we can take so much heart from," said Scully of the US which improved to a perfect 7-0 in 2018.
It was a sobering defeat for Scotland.
The Americans used their size and physical strength to overpower the Scots who ran out of gas in the second half and made too many costly errors with the game on the line.
"Give credit to America," said Scottish captain Stuart Hogg. "They really took their opportunities when they were there.
"We weren't good enough from the get-go. We scored a nice try early on and then we went to sleep."
Hooker Joe Taufete'e led the Americans with two tries and South African-born Germishuys scored a try to make it 28-24 and give them their first lead.
Scotland got off to roaring start with a try after just 59 seconds by Kinghorn and stretched that to 21-6 at one point before the Americans mounted a comeback.
The US came into the game with a 6-0 record this year, including a dominating 62-13 win over world No. 19 Russia in the first match of their three-game June test series.
The last time the USA battled Scotland was at the 2015 Rugby World Cup in England where they lost 39-16.
The US has been improving steadily since their loss to Scotland three years ago. They finished 3-6-1 in 2016 and 6-3-1 last year.
The US went with the same starting line-up against Scotland that they used in the Russia contest, while the Scots made 12 roster changes following their convincing 48-10 win over Canada last weekend.
Scotland will wind up their tour against Argentina next Saturday while the Eagles travel to Halifax, Nova Scotia to face Canada the same day.