The article Child Marriage in the United States: Prevalence and Implications from the Journal of Adolescent Health makes the following shocking claim right at the top:
We found that some 297,033 children were married in the U.S. between 2000 and 2018: 232,474 based on marriage-certificate data plus 64,559 based on estimates (Table 1). A few children were as young as 10 years when they married, but of those for whom age information was available, nearly all—96%—were aged 16 or 17 years.
In a country with a population of 300 million and change, this suggests that over an 18-year period, approximately 1 person in 1000 of the entire population became an underage bride or groom. (At a time when overall marriage rates are at an all-time low and declining, no less!) And if 96% of these (about 223,000) were 16- or 17-year-olds, there are a lot fewer of them than there are of the entire population.
A bit of back-of-the-napkin math with census data suggests there were probably somewhere between 2-3 million 16- and 17-year-olds in the USA in 2018. Divide that 223,000 by 18 and you have about 12,400 cases each year, or in other words, somewhere around 0.5% of all 16- and 17-year-olds in the country getting married every single year. (Yes, this is very oversimplified math, but the figures should be in the right ballpark.)
That seems a bit excessive to say the least. Is there any reason to believe these figures are anywhere near accurate? If not, how did the researchers manage to come up with such wildly wrong figures?