USA beat Canada while Brazil's Marta makes winning return
The Canadian team had threatened to go on strike last week due to their dispute over pay and contracts with the Canadian Soccer Association (CSA) before backing down after they were warned their action would not be legal.
The team are also demanding equal terms to the men's national side and captain Christine Sinclair had made it clear the team were playing under protest.
The team walked out ahead of the game wearing purple tee-shirts emblazoned with the slogan 'Enough is Enough' and before kick-off they formed a joint huddle with the US team.
American players, who reached a landmark settlement on equal pay and conditions with the men's team last year, have been vocal in support of the Canadians, many of whom play in the US with NWSL clubs.
But the gesture of solidarity did nothing to blunt the sharpness of the US team who attacked from the outset with Mallory Swanson forcing Canada keeper Kailen Sheridan into a near post save in the opening minute.
Sheridan was alert again to keep out an effort from Ashley Sanchez and it was no surprise when the Americans grabbed the lead in the seventh minute.
Alex Morgan, who had been honoured before kick-off to recognise her recently passing 200 national team appearances, laid off to Swanson who beat Sheridan with a sweetly struck effort from the edge of the box.
It was the fourth straight game in which Swanson has found the target.
Lindsey Horan headed against the post as the Americans pushed for a second which came in the 35th minute with Swanson on target again afer she intercepted a poor back pass from Vanessa Gilles.
Canada finally threatened just before the break with Janine Beckie's fierce drive forcing Alyssa Naeher into a diving save.
A stream of substitutions from both sides after the interval hampered the flow of the game but the US should have had a third when Ashley Hatch found herself in on goal but Sheridan was again up to the task.
Canada coach Bev Priestman felt her team's poor start to the game was at least partly influenced by the off-field stresses of the past week.
"We started flat and I think it's the result of you know the emotional (part) and the you know, training days lost," she said.
"I couldn't fault their effort. You just could see there was a flatness to them but.. this isn't fixed overnight, so we have got to push through. We've got to use this tournament for what's in front of us. We know we can't roll over, and nor will this group roll over," she added.
Marta's return
Earlier, Brazil's six-time World Player of the Year Marta made her return to action after a lengthy injury absence and promptly created the winning goal as Brazil beat Japan 1-0.
Marta suffered an ACL knee ligament injury in late March playing for her club Orlando Pride and missed the rest of last season.
The game was played at Orlando's Exploria Stadium and Brazil's Swedish coach Pia Sundhage threw on Marta as an 68th minute substitute in the opening game of the four-team tournament.
The 36-year-old took just four minutes to make her impact.
Cutting in from the left flank she spotted Debinha in space and slipped a low ball across the box which the striker confidently converted for her 58th goal in 133 appearances for Brazil.
Japan responded positively though and should have drawn level when Rikako Kobayashi was found with time and space in the box but wastefully shot over the bar.
Substitute Maika Hamano caused plenty of problems for the Brazil defence, the 18-year-old nearly levelling the scores with a fierce drive which crashed out off the bar.
The competition continues on Sunday in Nashville with the U.S facing Japan and Brazil taking on the Canadians.
All four teams are preparing for July's women's World Cup in Australia and New Zealand which runs from July 20 to August 20.
