During his visit to Latin America, Obama said on Saturday the allegations against Tim Tracy, 35, were "ridiculous."
But Interior Minister Miguel Rodriguez Torres insisted that intelligence agents tracking Tracy since late 2012 had uncovered ample evidence he was plotting with militant anti-government factions to destabilize Venezuela with violence.
"When you want to do intelligence work in another country, all those big powers who do this type of spying, they often use the facade of a filmmaker, documentary-maker, photographer or journalist," he told state TV.
"Because with that facade, they can go anywhere, penetrate any place."
Obama's comments about Tracy, and others questioning socialist leader Nicolas Maduro's democratic credentials after last month's disputed presidential vote, have infuriated the government and revived accusations of "imperialist meddling."
Late on Saturday, Maduro's government issued a formal protest note. In a remark reminiscent of his mentor and late Venezuelan president Hugo Chavez's tirades against U.S. leaders, Maduro even labeled Obama "the grand chief of devils".
Maduro, a 50-year-old former bus driver who rose to be Chavez's foreign minister and vice-president, has alternately railed against Washington in the same terms as Chavez and fanned prospects of a rapprochement by offering dialogue.
"I think he actually wants to improve relations with the north, but because he's vulnerable domestically right now, he needs to revive the old blood-and-thunder rhetoric to shore up support," said a Western diplomat in Caracas.
The Tracy case is a crucial test of Maduro's intentions towards a country that remains the main export market for the OPEC member's oil despite years of political hostility.
Friends and family of Tracy, who was a director and producer at Los Angeles-based Freehold Productions according to his LinkedIn profile, say he became passionately interested in Venezuelan politics and had excellent relations on both sides.
Interior Minister Rodriguez, however, countered that Tracy had "disguised himself" as pro-Chavez for credibility in some circles. Some 500 videos of him, and email exchanges with opposition activists, proved he was in the midst of violent plotting with students, Rodriguez added.
"In those videos, those radical, fascist kids ask the 'gringo' for dollars," he said.
U.S. diplomats have still not been able to visit Tracy in prison, where he awaits formal charges after being arrested in late April.
According to LinkedIn, he attended Georgetown University, and his work has included the "Madhouse" TV series about stock car racing for the History Channel, plus a just-finished comedy called "Angry White Man".