But Trump's wall was more like a sieve.
Exempted were thousands of residents of the Chinese territories of Hong Kong and Macau. Efforts to track US residents returning from mainland China were riddled with errors and broken communications.
An analysis of Commerce Department travel entry records and private aviation data obtained by The Associated Press shows that nearly 8,000 Chinese nationals and foreign residents of Hong Kong and Macao entered the US on more than 600 commercial and private flights in the first three months after the ban was imposed.
When US residents flying from mainland China arrived at US airports, the system meant to flag and monitor them for the development of symptoms lost track of at least 1,600 people in just the first few days the ban went into effect, according to internal state government emails obtained by the AP.
Trump's continuing travel restrictions on China, which he followed with a ban on travel from European nations in March and a new prohibition on entry from virus-plagued Brazil last month, remain the administration's first line of defence against foreign sources of the pandemic.
Trump on January 31 announced the original travel ban on any non-US residents who had recently been in mainland China. Travellers from Hong Kong and Macau were exempted from that ban, and they did not face the same enhanced screening and quarantine procedures required of Americans and others returning from Wuhan and China's mainland.
Flight records provided to the AP by FlightAware, an international aviation tracking company, show that more than 5,600 Chinese and foreign nationals from the two administrative zones flew to the US in February. Those totals dropped to 2,100 in March and just 150 in April, Commerce Department travel entry records show.
There is no clear evidence that the small but steady flow of people from Hong Kong and Macau introduced COVID-19 cases inside the US in January or in the four months since, but the exemptions “certainly undercut the purpose of the ban," said Dr Ronald Waldman, a professor of Global Health at George Washington University.
Waldman, who dealt with international quarantines as a Centres for Disease Control and Prevention official during a cholera outbreak in Africa in the 1990s, said travel bans can temporarily hobble the pace of a surging virus. Such moves “slow down the transmission and buy you time, but they have to be structured properly and followed with other strong measures".
None of the agencies involved in crafting and announcing the China ban -- the National Security Council, the State Department, the CDC and the Department of Health and Human Services -- would comment publicly to the AP about why Hong Kong and Macau were exempted. In a brief statement, the State Department said it would not “comment on internal policy decisions," and deferred to the White House. The White House did not respond to repeated requests for an explanation.
Officials familiar with the internal discussions that took place in late January before the China ban was announced cited concerns that a ban that was too broad might jeopardize trade talks and harm the travel industry. One official said the intent was to craft a ban that was “surgical" and would limit disruption.
A second administration official noted that the decision to impose a travel ban came after hundreds of thousands of travellers had entered the US from China in January. That same month, more than 12,700 people entered the US from the two Chinese territories, Commerce records show.
Hong Kong and Macau have long been given preferential economic and trade treatment from the US because of their financial importance and their status as independent enclaves within China's orbit.
When Trump's China travel restrictions went into effect on February 2, at least 15 cases of the new coronavirus had already been detected in Hong Kong, along with one death, and seven more cases had been found in Macau.
As of this week, the former British colony had registered 1,248 cases and seven deaths and Macau had 46 cases.
The CDC's warnings on Hong Kong and Macau have since been raised to the agency's highest alert level, urging Americans to “avoid all nonessential travel."
Separately, a less-heightened warning from the State Department urges Hong Kong travellers to “exercise increased caution."
If the flow of Americans going to Hong Kong and Macau was stifled, the stream of Americans and others coming back to the US from mainland China was unabated. And the programme to screen them had real problems.
Federal health officials planned to funnel the thousands of people returning from China through 11 airports for health screenings over the several weeks. Those with symptoms would be quarantined by the CDC.
The system was flawed to begin with. States could opt out of receiving passenger information from the CDC, and six did so: Georgia, New Jersey, Oregon, North Carolina, Arizona and Illinois. For the opt-out states, CDC simply disabled notifications. Any passengers from mainland China coming to their state would do so without being flagged or tracked.