In the introduction to the chart, Pew's researchers specifically noted that the U.S. ranked among the least restrictive of the included countries. But when the group isn't limited to the countries with the largest populations, the U.S. doesn't seem to fare as well. America has harsher restrictions than roughly 130 other countries. Places allegedly more free than the U.S. include Serbia, Haiti, and the Democratic Republic of the Congo—not exactly traditional strongholds of democracy.

This is the first sign that there's more to these rankings than one might guess on a first glance. Brian Grim, the lead researcher on this report, explained why it might actually be a good sign that the United States was ranked as more restrictive than some countries with historically weak track records on freedom.

In these kinds of places, a low government restriction score "could point to the fact that there aren't a whole lot of mechanisms in place to regulate anything in society," Grim said. "In some places, there just aren't government policies—the government isn't active."

What's different about the United States, he said, is that there are structures in place to address grievances: If a church community feels like it's experiencing discrimination, it can file a complaint with the Justice Department. Having a "low" level of restrictions is not very meaningful in unstable countries with weak or failed governments.

This isn't the case for all of the countries that got lower rankings than the United States. Grim pointed to Ireland as an example of a strong state with very low levels of government restriction on religious practice. "Even though there's been some favoritism of the Catholic Church, they have a long history of respecting the freedom of religion," he said. Still, Ireland's low ranking is at least partly explained by an accident of geography: Sectarian violence in Northern Ireland, which is technically part of the United Kingdom, doesn't count against the country's score, even though it is somewhat religiously motivated and historically tied to Irish independence.

The most interesting point of comparison Grim offered was France. Restrictions against body coverings, like the burkas and niqabs worn by some Muslim women, have raised the country's restrictions rating, placing it just above the United States in the "moderate" category. But, Grim said, some in France believe that the ban on religious garb actually promotes freedom: When the government was debating a ban on headscarves in public schools in 2004, French politician Fadela Amara argued that "the veil is the visible symbol of the subjugation of women."

This kind of tension also exists in the United States. Grim explained that local government decisions affected the country's rating quite a bit: Countless zoning laws, rulings on property rights, and restrictions on tax dollar use shaped the U.S. score. These weren't always clear-cut cases of religious restriction, either. "Sometimes there's a clear intent to try and keep a religious group out," Grim said. "Sometimes, it's more of a financial decision: [A city government might think], if we let this big church buy property in the center of the city, we're going to lose tax revenue."