Jurgen Klinsmann's men overcame a stern test from a dangerous Turkey side, building on Wednesday's 2-0 success over Azerbaijan with another impressive win.
Turkey wasted a number of openings in an entertaining game at the Red Bull Arena in Harrison, New Jersey, and their failings in front of goal proved pivotal as the hosts held on despite a late rally from Fatih Terim's charges.
Right-back Fabian Johnson put the USA ahead midway through the first half with an excellent opener, before Clint Dempsey doubled the lead seven minutes into the second half.
Turkey did pull one back in the 90th minute thanks to a Selcuk Inan penalty, but the home side stood firm.
The US will now face Nigeria on Saturday in Jacksonville before opening their World Cup campaign against Ghana on June 16.
It was Turkey who created the first chance of an open start to proceedings as they almost capitalised on some sloppy United States defending, Nuri Sahin curling an effort off the outside of the post from just inside the area after 11 minutes.
The hosts had the ball in the net four minutes later when Jozy Altidore converted from a corner, only for the strike to be disallowed for a foul in the box.
Turkey continued to have the better of the opening exchanges, though, and could have taken the lead when midfielder Inan fired high and wide with the goal seemingly at his mercy.
And the visitors were made to pay for their profligacy in the 26th minute as Klinsmann's side opened the scoring thanks to a fine goal from Johnson.
Johnson surged at the heart of the Turkey defence before laying the ball off for Michael Bradley, who then lofted an exquisite pass into the path of the Hoffenheim man to score with a confident low finish.
Chances dried up in the latter part of the first half, but the United States were gifted a second goal shortly after the interval.
Turkey defender Hakan Balta failed to deal with a low cross into the box from Brad Davis, presenting attacking midfielder Dempsey with the simple task of tapping in from point-blank range.
Terim's side were consistently wasteful in front of goal as they spurned a number of opportunities to get back into the game.
First Gokhan Gonul was denied by a fine save at the near post from USA substitute goalkeeper Brad Guzan, before Mustafa Pektemek lashed an effort wide.
Turkey did finally find a way through as Inan converted from the spot late on after Geoff Cameron had handled Pektemek's strike on the line, but they could not complete a comeback in injury time.
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