Since 2012, the American government has put more than $700 million into supporting gay rights groups and causes globally. More than half of that money has focused on sub-Saharan Africa — just one indication of this continent’s importance to the new policy.

America’s money and public diplomacy have opened conversations and opportunities in societies where the subject was taboo just a few years ago. But they have also made gay men and lesbians more visible — and more vulnerable to harassment and violence, people on both sides of the gay rights issue contend. The American campaign has stirred misgivings among many African activists, who say they must rely on the West’s support despite often disagreeing with its strategies.

“The Nigerian law was blowback,” said Chidi Odinkalu, chairman of Nigeria’s National Human Rights Commission and the senior legal officer for the Africa Program of the Open Society Justice Initiative, which supports gay rights on the continent. “You now have situations of gay men being molested on the streets or taunted. That was all avoidable.”

Fierce opposition has come from African governments and private organizations, which accuse the United States of cultural imperialism. Pressing gay rights on an unwilling continent, they say, is the latest attempt by Western nations to impose their values on Africa.

In retrospect, Father Ehusani said that Nigeria’s law was too punitive and an “overkill.” Without the American pressure, he said, “the law would not have come in the form in which it did.”

“The U.S. support is making matters worse,” said Mike, 24, a university student studying biology in Minna, a town in central Nigeria who asked that his full name not be used for his safety. “There’s more resistance now. It’s triggered people’s defense mechanism.”

“Before, these people were leading their lives quietly, and nobody was paying any attention to them,” Ms. Iwuagwu said. “Before, a lot of people didn’t even have a clue there were something called gay people. But now they know and now they are outraged. Now they hear that America is bringing all these foreign lifestyles. They are emboldened by the law. The genie has already left the bottle.”