A penalty in the 68th minute, controversially awarded but confidently converted by Carli Lloyd, broke the deadlock after Germany's Celia Sasic had missed a penalty of her own.
WATCH the key moments from USA v Germany:
The moments that defined #USA v #GER!! #USAGER #SBSTWG #FWWC2015 http://t.co/qVeSdjLGFc — SBS - The World Game (@TheWorldGame) July 1, 2015
Substitute Kelley O'Hara then stabbed in the second goal to ensure Jill Ellis's side will face England or Japan in the final.
Melanie Leupolz headed over from an early Germany corner and Alexandra Popp's mishit cross was pushed over by Hope Solo, while Nadine Angerer saved Julie Johnston's header at the other end.
Angerer denied Alex Morgan one-on-one after the striker was sent clear by Tobin Heath's excellent throughball.
15' @alexmorgan13 (#USA) goes through but @NAngerer (#GER) #GER #USA 0-0 #GER Watch LIVE http://t.co/MCAE4yBtyF http://t.co/p4hu3eIbcY — SBS - The World Game (@TheWorldGame) June 30, 2015
Popp and Morgan Brian both required lengthy treatment after a clash of heads as the USA player bravely cleared a free-kick.
Germany's Leonie Maier then became the first player booked, after fouling Megan Rapinoe.
Meghan Klingenberg's shot was headed away by defender Saskia Bartusiak, hopelessly wrong-footing Angerer but looping well wide. That led to three successive corners, with Morgan and Heath denied in the six-yard box from the second.
USA defender Becky Sauerbrunn was booked for hacking down Anja Mittag before Morgan wasted a good chance, side-footing wide with Heath better placed.
Heath was shaken after colliding with the advertising boards, while Popp somehow escaped a booking after flattening Rapinoe.
Popp re-emerged with her head extravagantly bandaged and her rugged and direct style earned Germany a penalty on the hour - Johnston booked for what would be termed a 'horse-collar' challenge in the NFL parlance of her boyfriend, Philadelphia Eagles tight end Zach Ertz.
Sasic had scored two spot-kicks in the tournament, including in the shootout against France in the quarter-final, but she side-footed this one wide as Solo dived the wrong way.
60' Sasic (#GER) sends her penalty wide!! #USA 0-0 #GER Watch LIVE http://t.co/MCAE4yBtyF #USAGER #SBSTWG http://t.co/qzU2ZVZuxJ — SBS - The World Game (@TheWorldGame) July 1, 2015
USA was given its own opportunity from the spot eight minutes later, though Annike Krahn's foul on Morgan was outside the area. That did not bother Lloyd as she stepped up to find the top corner for her third goal in successive games.
69' GOAL!! @CarliLloyd (#USA) drills home from the spot #USA 1-0 #GER Watch LIVE http://t.co/MCAE4yBtyF #USAGER http://t.co/cgdj7cToif — SBS - The World Game (@TheWorldGame) July 1, 2015
USA made victory safe with six minutes to go when Lloyd jinked through and fired the ball across goal and O'Hara, on for Heath in the 75th minute, flew in to score her first international goal.
84' GOAL!! Super sub O'Hara doubles #USA's lead! #USA 2-0 #GER Watch LIVE http://t.co/MCAE4yBtyF #USAGER #SBSTWG http://t.co/zJIyHpL0IZ — SBS - The World Game (@TheWorldGame) July 1, 2015
England and Japan meet in Edmonton with the winner facing USA in the Vancouver showpiece.
