Solve the following sql problem:
In 2019, how many users in the United States have a family history of mental illness?

Schema:
SCHEMA:
- Table: Question
  - Column: questiontext
    - Samples: [What is your age?, What is your gender?, What country do you live in?, If you live in the United States, which state or territory do you live..., Are you self-employed? (truncated)]
  - Column: questionid
    - Samples: [1, 2, 3, 4, 5]
- Table: Survey
  - Column: SurveyID
    - Samples: [2014, 2016, 2017, 2018, 2019]
  - Column: Description
    - Samples: [mental health survey for 2014, mental health survey for 2016, mental health survey for 2017, mental health survey for 2018, mental health survey for 2019]
- Table: Answer
  - Column: AnswerText
    - Samples: [37, 44, 32, 31, 31]
  - Column: SurveyID
    - Samples: [2014, 2014, 2014, 2014, 2014]
  - Column: UserID
    - Samples: [1, 2, 3, 4, 5]
  - Column: QuestionID
    - Samples: [1, 1, 1, 1, 1]

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'