This is a 2018 study by Yale,现在说两千万可能都说少了

Generally accepted estimates put the population of undocumented immigrants in the United States at approximately 11.3 million. A new study, using mathematical modeling on a range of demographic and immigration operations data, suggests that the actual undocumented immigrant population may be more than 22 million.

 

https://insights.som.yale.edu/insights/yale-study-finds-twice-as-many-undocumented-immigrants-as-previous-estimates