In its annual survey of religious discrimination, the State Department said that, while many governments had worked harder to end abuses, extremist non-state actors like the Islamic State group are on the rise.
And discrimination is not limited to Washington's foes and rivals like Iran and China but is "egregious" in close allies like Saudi Arabia and worrisome even in Western democracies like France and Germany.
"No nation can fulfil its potential if its people are denied the right to practice, to hold, to modify, to openly profess their innermost beliefs," Secretary of State John Kerry said as the report was unveiled.
"We hope to give governments an added incentive to honor the religious dignity of their citizens."
The "International Religious Freedom Report" has no direct impact on US policy towards the countries it studies, but Kerry said it would serve as reference for diplomats and activists lobbying for change.
In the 12 months since the last report, the most serious religious persecution has been carried out by jihadist groups like the Islamic State in Iraq and Syria and Boko Haram in Nigeria and the Lake Chad Basin.
"Under their control, captives have been given a choice between conversion or slavery or death," Kerry said.
"Entire populations of religious minority groups have been targeted for killing. Terrified young girls have been separated out by religion and sold into slavery."
The author of the report, Washington's special envoy for religious freedom, Ambassador David Saperstein, cited the fate of the Yazidi, Christian and other religious minorities in northern Iraq as particularly severe.
"There's been a Christian community there for 1,600 years, across the Nineveh Plain church bells have pealed for 1,600 years. Today they are silent," he said.
"We're not going to rest until people have a right to live out their religious lives back in their home communities in accordance with their conscience."
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As it had last year, the report also noted a rise in anti-Semitic rhetoric and attacks in France, Germany and elsewhere in Europe despite efforts -- acknowledged by Saperstein -- by local authorities to contain it.
Some of the hostility towards European Jews has been associated with campaigns against Israel's occupation of Palestinian territory, but Washington thinks much of this has crossed the line into outright bigotry.
- Crossed the line -
"Criticism of the public policy of any nation ... that's appropriate. That's part of the free marketplace of ideas and discourse," he said.
"Where it has often crossed the line is where groups have tried to argue that Israel is an inherently illegal state -- that it doesn't have a right to exist as a Jewish state," he said.
Saperstein condemned efforts to "de-legitimize" the Jewish state, and argued that: "It's right on the cusp of that line when it holds one country to different standards than it would hold another country.
"We normally think of that as racism and we feel that when it steps over that line then it constitutes anti-Semitic activity and not just legitimate discourse about Israel's policies," he said.
The report itself warned that "a surge in anti-Semitism in Western Europe during 2014 left many pondering the viability of Jewish communities in some countries."
It cited a reported 101 percent increase in anti-Semitic acts in France between 2013 and 2014 and said the number of French Jews choosing to move to Israel had doubled.
In Germany, mainstream public figures spoke out against anti-Semitism, but attacks increased "especially in the summer, when there were numerous protest demonstrations against the Gaza conflict."
The report also criticized both US ally Saudi Arabia -- a Sunni monarchy with a fundamentalist clergy -- and its regional enemy Iran -- a Shiite Islamist republic.
"Both of those countries have structural, systematic, egregious violations," he said.