Rapinoe was coming back from an ACL tear. She had not played in eight months prior to the Olympics. The decision to include her on the roster was controversial. She was clearly not 100 percent. That said, I agree that, given her age, she is questionable for the next World Cup.
The U.S. went into the last World Cup as the oldest team in the field. That was a mistake, and I don't expect it to happen again. The next two years are the time for introducing new players. Rapinoe has a shot, but when player selection comes down to a close call, team management has to have the strategic discipline to give the nod to the younger player. Players already over 30 will be mid-30's by the time the next World Cup begins and, if the coaches have their heads on straight (never a sure thing), they should have to be clearly superior to hold their positions.
Whether that factors into Rapinoe's thinking now, I don't know, but it might. She probably does see the end of the line looming ahead and figures she has relatively little to lose. She is making herself a problem for U.S. Soccer. The USWNT players have done a pretty good job over the years of keeping their public personas squeaky clean (with one big, out of control exception). That's especially important because the U.S. women are trying to build a viable league, and dragging politics onto the field is poison. U.S. Soccer put out a pretty stiff statement about standing for the national anthem. Rapinoe is inviting disciplinary action.
Look at the stands no one there to care or pay her salary