The visa waiver program currently includes 38 nations, primarily in Europe and Asia, regarded as not representing an immigration risk. H.R. 158 would require previously eligible travelers who had recently visited Iran, Iraq, Syria, or Sudan to go through a full visa application process. The bill would also require waiver partner countries to adopt electronic and biometric passport systems.

The revisions are intended to target the thousands of citizens of visa waiver partner countries, particularly in Europe, who have reportedly traveled to conflict zones for terrorist training. But by some interpretations, it would also place restrictions on European citizens whose national origins lie in those countries, even if they had never visited them.

Specialists in international business travel and immigration also said that the bill could have serious and widespread unintended consequences, potentially impacting all Americans’ ability to travel internationally.

The problem is not so much with the program itself, but its wider diplomatic impacts.

“Any changes to the visa waiver program are going to be perceived outside of the United States as political,” says lawyer Douglas Hauer, whose practice encompasses both the financial and immigration dimensions of international deal-making. “And we should anticipate that there could be harsher visa restrictions imposed on American citizens traveling outside of the U.S.”

Terror-related restrictions aren’t exempt from the principle of reciprocity in immigration. Brazil, for example, imposed higher immigration burdens on Americans after the U.S. restricted Brazilian travelers after 9/11. The current bill gives the Department of Homeland Security special power to remove countries from the visa waiver program if they fail to comply with new requirements, making its ultimate impacts hard to gauge.

Stricter visa requirements, which often entail travel to consulates, entry interviews, and fees, could substantially hamper international business, says Hauer. “A transaction might move a million miles a minute, and people need to travel,” he says. Even under the current relatively free system, he has seen many deals delayed by immigration problems.

All of which might even be worth it—if the proposed bill was likely to work.

According to Hauer, the current bill relies on voluntary disclosure of visits to barred countries. “If someone wants to conceal that information, they can conceal it,” he says.

Visa processing also could be a problem. “The question remains whether the U.S. State Department will have enough resources to complete additional screenings and issue the appropriate visas in a timely manner,” says Said Boskovic, global director of immigration services for Crown World Mobility, an executive travel firm.

Visa screening interviews currently can last as little as a minute, and many U.S. consulates are severely understaffed. Hauer argues that by adding more load to the system, with no additional funding, H.R. 158 could actually make those interviews even less effective. State Department staffers could also begin to deny or indefinitely delay a larger number of visas.

“I think there’s a strong political dimension to it,” Hauer says of the proposed changes. “The visa waiver program isn’t bringing hundreds of terrorists into the United States. The visa waiver program is facilitating business.”

Some House members seem to share that skepticism. On Friday, more than 30 of them signed a letter to Senate leadership urging removal of elements seen as imprecise and discriminatory. The bill is still widely expected to pass the Senate as part of an omnibus package, and to be signed by the president.

Airbnb is trying to make life easier for business travelers and their hosts. See how in this Fortune video:

Subscribe to Data Sheet, Fortune’s daily newsletter on the business of technology.