But that outcome alone would not improve America's score on the organization's Girls' Opportunity Index, said Miles. To do that, she said, women would have to occupy more seats across all levels of government.
"In many countries, women who make it into those high levels of government act as role models and incentivize girls to enter into public service," Miles said. "It's going to have to be more than Hillary Clinton getting elected."But that outcome alone would not improve America's score on the organization's Girls' Opportunity Index, said Miles. To do that, she said, women would have to occupy more seats across all levels of government.
She did add, however, that a woman in the White House "would be good for getting attention to policies that benefit women and girls."
In addition to its low levels of women in government, the U.S. also performs poorly next to other wealthy countries when looking at rates of teenage births and maternal mortality — both of which are higher among women of color, Miles said.
Though teenage birth rates have been falling in recent years, there are still about 24 births per 1,000 women between the ages of 15 and 19, according to data compiled by the World Bank. Sweden sees just 6 births per 1,000 women in the same age range, the data found.
Maternal mortality rates similarly show the U.S. coming up short. There were 14 deaths of women in the U.S. per 100,000 live births in 2015, according to the World Bank's data, up from 12 per 100,000 in 1990. Meanwhile, there were four deaths in Sweden per 100,000 live births in 2015, down from eight in 1990.
Based on the data Save the Children used in its evaluation, the U.S. falls behind countries with a history of violent conflict (Algeria, ranked 31), authoritarian regimes (Kazakhstan, ranked 30), economic strife (Greece, ranked 26), and direct action against women's rights — such as Poland, number 22, where tens of thousands of women took to the streets last week in protest of a near-total abortion ban. (Poland's ruling Law and Justice part subsequently withdrew its support of the draft proposals.)
For those reasons, Miles said she expects there to be some pushback against America's position in Save the Children's ranking. But it's a conversation she said she welcomes.
"Part of the challenge in the U.S. is that we have such inequality gaps, and so I think the numbers are what the numbers are," said Miles. She admitted even she was surprised to see where the U.S. fell compared to some other countries, initially thinking to herself: "Can that be?"
All 10 countries at the bottom of Save the Children's ranking are in Africa, where child marriage remains a widespread problem.
In Niger, the worst country for girls on the organization's list, 76 percent of women are married before age 18, according to the report.
Some, like 15-year-old Salaha, who wished to only be identified by her first name, are lucky. When a stranger asked her for her hand in marriage two years ago, she refused, afraid of needing a C-section during childbirth like many of her peers.
Her parents were supportive and allowed her to stay in school, she told NBC News by phone, via an interpreter. But she wants the international community to know that other girls in her country don't get the same opportunity.
"She wants parents and people to be advised to stop the practice of early marriage," Salaha's interpreter said. "She wishes all the girls of her age could go to school and become teachers or another model of success in their communities."