An unusual alliance of civil libertarians, far-left liberals, and conservative television commentators has sprung up in opposition to a bipartisan bill now floating around in the U.S. Senate intended to curb the online influence of America’s “foreign adversaries” by giving the commerce secretary broad powers to ban foreign technology like China’s TikTok app.

While the bill doesn’t mention the company specifically, it is one of three now before Congress aimed squarely at TikTok. Backers of the bill, dubbed the Restrict Act, say it would give the government broad authority to ban apps originating in a number of countries deemed American enemies, including China, Russia, North Korea, Iran, Cuba, and Venezuela.

The bill, introduced by Senators Thune and Warner, a Republican and a Democrat, enjoys broad bipartisan support in the Senate, and also has been endorsed by the White House, which has otherwise remained relatively mum on the TikTok issue so far.

“This bill presents a systematic framework for addressing technology-based threats to the security and safety of Americans,” the national security advisor, Jake Sullivan, said. “This legislation would provide the U.S. government with new mechanisms to mitigate the national security risks posed by high-risk technology businesses operating in the United States.”

Those “new mechanisms” are not going over well among civil libertarians and others skeptical of giving the government additional powers. A broad array of civil libertarians, conservatives in the House, crypto-enthusiasts, and left-wing activists are raising alarm bells about some of the provisions in the legislation.

“This bill isn’t really about banning TikTok,” a Fox News host, Tucker Carlson, said on his show Monday. “It’s never about what they say it is. Instead, this bill would give enormous and terrifying new powers to the federal government to punish American citizens and regulate how they communicate with one another.”

Over at the left-wing Daily Kos, headlines are screaming that the act is a “smokescreen for the Patriot Act 2.0.” Republicans on the House Financial Services Committee last week called it a “smokescreen for the largest expansion of executive power” in decades.

In an op-ed in Wednesday’s Louisville Courier-Journal, Senator Paul of Kentucky excoriated his fellow lawmakers for pressing legislation to ban TikTok after complaining for years that American-owned social media companies have censored conservatives. “If you don’t like TikTok or Facebook or YouTube, don’t use them,” Mr. Paul said. “But don’t think any interpretation of the Constitution gives you the right to ban them.”

Some of the alarmists are convinced that the bill would outlaw Americans’ use of virtual private networks, or VPNs, to bypass a national ban on TikTok or other technology created by a foreign adversary, which Mr. Warner’s office has explicitly ruled out. Under the terms of the bill, his office said, in order to be subject to any kind of penalty, someone must be engaged in “sabotage or subversion” of American communications technology products and services, creating “catastrophic effects” on America’s critical infrastructure, or “interfering in, or altering the result” of a federal election.

“To be extremely clear, this legislation is aimed squarely at companies like Kaspersky, Huawei and TikTok that create systemic risks to the United States’ national security — not at individual users,” Mr. Warner said in a statement.

Mr. Warner’s assurances aside, the language in the bill is sufficiently fuzzy to justify some of the concerns being bandied about online. As written, it would give the commerce secretary and the director of national intelligence — the executive branch, in other words — unilateral power to decide who or what is a “foreign adversary” and broad power to “identify, deter, disrupt, prevent, prohibit, investigate, or otherwise mitigate … any risk arising from any covered transaction by any person, or with respect to any property.”

If the bill is passed as is, analysts believe it would give the executive branch the power to ban any number of technologies connected to those foreign adversaries. Law enforcement would have the power to go after people who collaborated with these foreign entities, and impose minimum sentences of 20 years and hundreds of thousands of dollars in fines on those convicted of such actions.

The law is currently sitting in the Senate Commerce Committee and its immediate future is unclear. Aides on the committee told the Washington Post that the language of any legislation intended to curb TikTok is preliminary, and that discussions are ongoing. Among the many voices urging Congress to put the Restrict Act aside and try another way is that of a former libertarian congressman, Justin Amash.

The bill “isn’t about banning TikTok,” Mr. Amash said on Twitter. “It’s about controlling you. It gives broad powers to the executive branch, with few checks, and will be abused in every way you can imagine.”