So much for that nonsense about Omar Mateen being an "American". He was a foreigner who happened to be born in the United States. His native language was Afghani and he attended an Islamic school.
Enrolling in St. Lucie Elementary in December 1991, Mateen was sent to finish kindergarten at Frances K. Sweet Elementary because he was limited in reading, writing and speaking English, according to documents.
Mateen’s first language was “Afghani,” which was primarily spoken at home, according to records.
And he had attended an Islamic school.
He already had attended two kindergartens — one in an Islamic school in Westbury, N.Y. — before his family moved to Florida in 1991.
He didn't do well in non-Islamic institutions, making threats and being generally disruptive. Which is about what you might expect from a very different culture. In the EU phrasing, Omar was never integrated. He was effectively a foreign immigrant who never became American and hated America. There was nothing American about him.