appears "Population of Vatican City" was estimated by ChatGPT for this table. I suspect they're not quite as fond of radios as all the islanders for whom that license is important
This is a weird set of metrics because ARRL reports per FCC counts 756,828 licensed ham radio operators. This lists 333,287,557. So this is either way wrong at 333million or of all time including dupes like people who were issued call signs and now SK or who abandoned old call signs and have new call signs.
That's the population, not the number of radio operators. The number of call signs given for the USA is 1635406, or about 2.2 per (currently) licensed operator.