That's because individuals receiving less than $100 in unemployment assistance through regular state programs aren't eligible, according to the executive order that Trump signed Aug. 8.
Estimates suggest that the clause disproportionately affects women, many of whom are among the lowest-paid workers.
According to Eliza Forsythe, a labor economist at the University of Illinois, about 1.5 million Americans, or roughly 6% of an estimated 28 million unemployment insurance recipients, could be excluded just as financial protections for renters, homeowners and small businesses lapsed.
"Under $100 a week in benefits is impossible to live on, and it's cruel to] single out these workers to deny benefits to," Forsythe wrote in a tweet.
For Americans who do qualify for the aid, how much money they'll receive depends on which state they live in. Unlike the previous $600-a-week supplement, which was fully federally funded, Trump's plan requires states to pick up 25%, or $100, of the $400-a-week aid.
Rather than adding $100 a week on top of what they already pay in weekly benefits, states can count their existing payments toward the 25% share, according to guidance from the Labor Department. Most workers are expected to receive a $300 boost rather than the intended $400.
The Federal Emergency Management Agency, which is distributing the money, has already approved 11 states for the program: Arizona, Colorado, Idaho, Iowa, Louisiana, Maryland, Missouri, Montana, New Mexico, Oklahoma and Utah. Of those, Arizona is the first to have started making the payments.
South Dakota has rejected the $300-a-week aid: Last week, Gov. Kristi Noem, a Republican, said workers did not need the help, citing the state's economic recovery from the virus-induced recession.
The average state unemployment benefit is about $330 per week. With the federal supplement, Americans can expect to receive about $630 in weekly unemployment benefits.
The Labor Department's July jobs report released last Friday showed that employers added 1.8 million jobs in July, sending the unemployment rate down to 10.2%. While it marked the third consecutive month of job growth in the millions, the economy has so far added back less than half -- about 42% -- of the 22 million jobs it lost during the pandemic.
There are roughly 10.6 million more out-of-work Americans than in February.