-- Database schema
| Question : questiontext [ TEXT ] , questionid [ INTEGER ] primary_key | Survey : SurveyID [ INTEGER ] primary_key , Description [ TEXT ] | Answer : AnswerText [ TEXT ] , SurveyID [ INTEGER ] , UserID [ INTEGER ] , QuestionID [ INTEGER ] |
-- -- In 2019, how many users in the United States have a family history of mental illness?

SELECT COUNT(T1.UserID) FROM Answer AS T1 INNER JOIN ( SELECT T2.questionid FROM Answer AS T1 INNER JOIN Question AS T2 ON T1.QuestionID = T2.questionid WHERE T1.SurveyID = 2019 AND T2.questionid = 6 AND T1.AnswerText LIKE 'Yes' ) AS T2 ON T1.QuestionID = T2.questionid WHERE T1.SurveyID = 2019 AND T2.questionid = 3 AND T1.AnswerText LIKE 'United States';