Stuart McInally has been named captain in the absence of John Barclay and Greig Laidlaw, who have both been given the summer off.
Harlequins midfielder James Lang, capped by Scotland at age grade, is included despite having previously declared for Wales.
Townsend said: “There are twin goals for this tour - the first is to build on the work we’ve done so far this season and finish with improved performances.
“We also have the Rugby World Cup in our thoughts, as this will be our last tour before we leave for Japan next year.
“Touring and staying together for four weeks and experiencing different environments will be very informative - seeing how players get on with each other, how much they improve and how they rise to each challenge we face on tour.”
A number of regulars have been given an extended break, with Barclay and Laidlaw among those rested. Unavailable through injury are Luke Crosbie, John Hardie, Huw Jones, Willem Nel and Hamish Watson.
Notable absentees include Jonny Gray, Sean Maitland, Gordon Reid, Finn Russell, Tommy Seymour and Ryan Wilson.
Scotland face Canada at the Commonwealth Stadium in Edmonton, on June 9; the USA at the BBVA Compass Stadium in Houston on June 16 before taking on Argentina on the weekend of June 22 at the Estadio Centenario in Resistencia.
Simon Berghan, Jamie Bhatti, Magnus Bradbury, Fraser Brown, Lewis Carmichael, Allan Dell, David Denton, Matt Fagerson, Zander Fagerson, Grant Gilchrist, Richie Gray, Luke Hamilton, Murray McCallum, Stuart McInally, Jamie Ritchie, Tim Swinson, Ben Toolis, George Turner.
Alex Dunbar, Nick Grigg, Chris Harris, Adam Hastings, Sam Hidalgo-Clyne, Stuart Hogg, George Horne, Pete Horne, Ruaridh Jackson, Lee Jones, Blair Kinghorn, James Lang, Byron McGuigan, Ali Price, Duncan Taylor.