A tumultuous year is on the horizon for TikTok in the United States as anti-China Republicans gain more control in Congress, sparking calls for greater surveillance of the hugely popular video-sharing app.

Owned by Chinese tech giant ByteDance, TikTok has become a political punching bag for U.S. conservatives who allege that the app downloaded by millions of U.S. young people can be circumvented for spying or propaganda by the Chinese Communist Party (CCP).

But now Democrats have joined the groundswell of criticism and U.S. President Joe Biden last week signed a new law that bans the use of TikTok on government-issued devices. The law also bans TikTok use in the U.S. House of Representatives and Senate.

TikTok is the equivalent of "digital fentanyl," said Republican lawmaker Mike Gallagher, one of the leading voices in Congress against China, comparing the app to the deadly opioid.

"It's highly addictive and destructive and we're seeing troubling data about the corrosive impact of constant social media use, particularly on young men and women here in America," he told NBC News.

"We have to ask whether we want the CCP to control what's on the cusp of becoming the most powerful media company in America," Gallagher told NBC.

A TikTok spokesperson said that there is "zero truth" to Gallagher's comments and that the CCP "has neither direct nor indirect control of ByteDance or TikTok."

The national law matches dozens of government-use bans at the state and local level and now TikTok USA is fighting to survive as a Chinese-owned company, with the growing chance that it will have to divest from ByteDance in order to remain on U.S. smartphones.

This was the fate demanded by former president Donald Trump who ordered that TikTok operations in the United States be sold to U.S. company Oracle before Biden entered the office and took a less drastic approach.

But the mood towards TikTok soured considerably last month when ByteDance was forced to admit that employees improperly accessed TikTok data to track journalists to identify the source of leaks to the media.

Criticism has even expanded to other Western countries with French President Emmanuel Macron last month accusing the Chinese social network of censoring content and encouraging online addiction among young people.

Comprehensive package

TikTok has put months of effort into trying to find a long-term arrangement with the U.S. government through the secretive interagency Committee on Foreign Investment in the United States (CFIUS).

Reports have revealed that TikTok and the Biden administration were on the verge of announcing a long-term deal that would have defined strict safeguards for U.S. users' data.

"The solution under consideration by CFIUS is a comprehensive package of measures with layers of government and independent oversight... well beyond what any peer company is doing today," said TikTok's spokesperson Brooke Oberwetter.

But this arrangement has been held up amid public criticism by FBI Director Christopher Wray who said he continues to see TikTok as a threat to national security.

Wray last month warned the Chinese could control the app's algorithm, leaving U.S. users vulnerable to a government "that doesn't share our values, and that has a mission that's very much at odds with what's in the best interests of the United States."

TikTok staunchly denies that the Chinese government has such controls.