Well, my two cents worth is, that if we look historically where Christianity first flourished, it no longer flourished once Islam came in, it then vanished.
Wherever Islam goes, Christianity and other religions cease to exist any longer. That is a major concern.
Medieaval history shows us this with Turkey, Syria, Egypt and Palestine. All were once flourishing with Christians. Not now.
Also there is no reciprocation. Why should Islam come into the West, when the Orientals (the East Middle East) do not allow Christianity? That is unfair. But Christians being Christians will allow the unfair practice, because we are to live in humbleness of mind. Whereas Islam teaches a very proud spirit.
Most Western societies are liberal left, who only know too well communism will conquer Islam, so they don't worry about Christians. Islam's past shows them conquering Christians, and Communism's past shows them conquering Islam. What the future holds only Jesus Christ our Lord and Saviour knows.