In the United States, it's 73.7 percent.
It wasn't always like this. In the 1990s, as you can see above, the U.S. had as many working women, in percent terms, as France or Germany or Canada. But while those countries have continued to get more women into the workforce, the U.S. has stagnated and started losing ground in the 2000s. Why? Well, it's the child care, stupid. It costs a lot—$7,800 a year, on average—enough that, for a lot of couples, it might make more sense in the short-term for someone to stay home. That "someone" almost always means the woman, and, as Catherine Rampell points out, that "short-term" can be short-sighted. That's because women who take a break from work don't make as much down the line. Still, the fact that their after-tax earnings might barely cover the cost of childcare today, not to mention the fact that it's hard to find good caregivers, is enough to make a lot of women discount these future costs.
So should we give working parents tax credits or invest in universal pre-K? Yes. Having kids is expensive, and we, as a society, kind of have an interest in people doing it. If we're going to cut anybody's taxes, it makes sense to help parents out. The problem, though, is that giving parents more money doesn't help them like they need to be helped if there aren't good childcare options. And in a lot of places there aren't. That's where universal pre-K comes in. Now it's true that it isn't cheap, at around $150 billion over ten years. And it's also true that its educational benefits tend to get oversold. But that doesn't mean it's not worth it. A Brookings paper found that high-quality preschools in Oklahoma got more low-income women working and spending more time reading with their kids. It didn't get more women working overall, though. And that's why we can't afford to just try this or that if we want to make it easier to have a family and a career. We have to try everything.
Because if Japan thinks it has a working women problem, then what do we have?