Chinese Paramilitary police officers salute each other as they stand guard below a portrait of the late leader Mao Zedong in Tiananmen Square in Beijing, China.

AMID AMERICA'S fractious political landscape, where cross-party trust is all but absent and bombast seems the currency of the day, concern is growing that wariness about foreign influence from Russia and China is morphing into paranoia.

The latest example came this month when two top Republicans on the House Natural Resources Committee accused the nonprofit Natural Resources Defense Council in a letter of acting as an agent of China and demanded that the environmental advocacy group turn over internal documents.

The NRDC has vigorously refuted the allegations, declaring it is "proud of our work, in China and elsewhere."

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The letter, experts say, seemed aimed not so much at rooting out Chinese influence as smearing the environmental movement at large by associating it with foreign adversaries. It was sent at a time when alarm about covert foreign influence in the U.S. occupies a space in American political dialogue perhaps not seen since the Cold War and Sen. Joe McCarthy's rabid investigation of artists, activists and labor to discern whether communists and communist sympathizers were trying to undercut American institutions amid a wider Red Scare.

"There are a whole lot of other organizations you could find, so why would you pick one like this, where it would be a public slog and one where people would really disagree with you?" says Abigail Grace, who until recently served on the National Security Council staff under President Barack Obama and President Donald Trump. "Politicization of this is going to be a way for us to end up in a 1950s McCarthyist situation very quickly."

Of course there are differences. Communism in both Russia and China has long since given way to forms of authoritarian capitalism, so rather than rivalries based on competing ideologies, the tension is more emblematic of a recent return to economically driven great power politics. China, for its part, has been accused of rampant industrial espionage and massive theft of U.S. government information, while Russia's broad agenda of destabilization set its sights on influencing the presidential election.

But the renewed hostilities between America and two of its most recent adversaries – and the audacity of their violations – have created a domestic climate in which nearly any association with the countries is politically toxic.

Democrats have long sought to exploit the situation at the highest level, suggesting President Donald Trump is in the service of Vladimir Putin, with presidential nominee Hillary Clinton famously calling Trump a "puppet" of the Russian president during a 2016 debate. The notion that Trump could be a "Manchurian Candidate" has loomed over the work of special counsel Robert Mueller, whose investigative team has established ties between Russian interests and people involved in Trump's campaign.

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Russia was the impetus for the Democrats to urge the Federal Election Committee – so far unsuccessfully – to develop new guidance to prevent foreign spending on U.S. elections, after it was revealed that Moscow used social media platforms like Facebook to spread propaganda.

And Senate Democrats have gone after one of their favorite targets, the National Rifle Association, with a Russia-themed twist, accusing the group of being a pawn of Moscow and of being a pass-through for Russian funding of the 2016 elections. The FBI is reportedly investigating whether the organization illegally directed money from a top Kremlin-linked banker toward Trump's presidential campaign.

In the current climate, even developments that might not have drawn much attention are getting headlines when a connection to Russia is introduced. Green Party presidential candidate Jill Stein, for example, found herself having to answer for an appearance in the company of Putin in 2015. And an analyst on MSNBC earlier this year asked a congressman whether the Republican chairman of the House intelligence committee had been "compromised by the Russians."

Internationally, it's much the same story, with European political parties facing accusations about the nature and extent of their ties to Moscow, while the implications loom uncomfortably over any such disclosure.

In the U.S., as Trump fends off the Mueller probe and touts the benefit of repairing fraught ties with Moscow, Republicans have struggled to distance themselves from Russia, dampening their criticism of the Kremlin. While some have not been shy about turning Russia to their advantage – even this year attributing protests of environmental policy to Russian meddling – to a large degree, the GOP has instead turned its concerns about foreign influence on China in particular.

"The Russian case has gotten all caught up in American domestic politics, and that has, to a certain degree, diluted and distracted attention from the Russians because there are so many conservatives who are just denying that there is any real Russian effort to try to undermine the election, because that would reflect poorly on Trump," says Michael Swaine, a senior fellow at the Carnegie Institute for International Peace. "So there's a logical resistance to looking at the Russians too closely, for political reasons. That doesn't exist in the Chinese case."

Sen. Marco Rubio of Florida, in particular, has focused on rooting out Chinese influence operations: Last month he published an op-ed in The Washington Post warning of "China's malevolent economic behavior" and sent a letter to the Wilson Center , a federally funded nonpartisan think tank in the nation's capital, asking about the political affiliation of a guest speaker on a panel that the center planned to hold on Chinese influence operations.

Discerning the line between legitimate worry and overblown paranoia, however, has proved to be a challenge. Robert Daly, a former diplomat to China who now directs the Kissinger Institute on China and the United States at the Wilson Center, says that the letter to the NRDC is particularly troubling.

"Where does this stop? Can American organizations work to promote human welfare, regardless of our legitimate geo-strategic concerns, or not?" Daly says. "We're in a global competition for leadership with China. Do we really mean that Americans cannot also work, in an apolitical way, to advance human welfare in China?"

China's activities in the U.S. are understood to range from espionage and targeted efforts to influence particular individuals, to broader information campaigns aimed at burnishing China's image in the U.S.

"It runs all the way from pretty threatening to pretty benign," Swaine says.

FBI Director Christopher Wray, for example, testified before a Senate panel in February that the bureau is concerned about Chinese influence on college campuses. Confucius Institutes, for example, which are funded by Beijing and partner with American universities, are seen as vehicles for exerting Chinese influence in the U.S.

But Wray's remarks also provoked outrage from Chinese student associations and Asian advocacy groups, which warned of having "every Chinese student or scientist assumed guilty until proven innocent of a national security threat."

And just last month, after the president defied even those in his own party by offering a lifeline to a Chinese telecom company that the intelligence community says poses a national security risk, more than 60 Democratic lawmakers responded by seeking an ethics investigation into Trump's business practices with China.

With public concern heightened about the intentions of Beijing and Moscow, experts who spoke with U.S. News say that the letter sent to the NRDC suggests that U.S. organizations are now facing the prospect of similar scrutiny – and may signal the rise of a new tactic that brands perceived political opponents as Chinese or Russian fronts.

"Of course, that's what's going to happen. That's what happens in a McCarthyist witch hunt. This is the template, right?" says Kaiser Kuo, a freelance writer and former director of international communications for the Chinese search engine Baidu, who frequently writes about and hosts a podcast on China. "I don't think it's risen to that yet. But we're teetering toward it. And I do worry."