Van der Merwe equals try record as Scotland storm past lowly USA
South African-born wing van der Merwe raced over for Scotland's opening try in a one-sided Test match at Audi Field in Washington D.C.
His score saw him draw level with Stuart Hogg as Scotland's record try-scorer in international rugby.
However, despite Scotland's dominance, van der Merwe was unable to pull clear of Hogg at the top of the rankings.
Instead, it was left to Ewan Ashman to snaffle the try-scoring glory, with the Canada-born hooker grabbing a first-half hat-trick.
All of Ashman's first half points arose from driving mauls from the lineout as Scotland punished US indiscipline.
After van der Merwe's early try, Ashman rumbled over for his first score in the 19th minute after Scotland opted for an attacking line-out, with fly-half Adam Hastings converting.
Ashman's second score was almost a carbon copy, with the hooker once again driving over from a line-out after a US penalty, Hastings converting to make it 21-0.
The US, meanwhile, finally got on the board soon afterwards once they forced a turnover after a Scotland scrum near their own line.
The ball was transferred to center Tommaso Boni who barged over for a deserved score. Fly-half A.J. MacGinty added the conversion.
On the stroke of half-time though, Scottish forward pressure once again took its toll, with Ashman completing his hat-trick after dotting down from another driving maul to make it 28-7 at the break.
An improved US defensive display in the second half staunched the flow of Scottish points, but the tourists were nevertheless able to extend their lead through converted tries from scrum-half George Horne and No.8 Matt Fagerson.
Friday's game was the second of Scotland's four-match tour of North and South America. The Scots face Chile in Santiago on July 20 before taking on Uruguay in Montevideo on July 27.