Well, bear in mind, N. Syria is not all Muslim. In fact within the Kurd community and the Syriac community it is a minority.
Among N,. Syrian Kurds there may be a division on religious basis something like 1/3 atheist, 1/3 Muslim (may be less) and 1/4 Christian (possibly more). Remainder Ezidi.
Turkey is probably 98% Muslim (many in name only). Those who admit other than Muslim are seriously disadvantaged by the government.
Iraq was 95% Muslim (75% Sunni, 25% Shia division), possibly 5% Christian, Ezidi or Atheist.
Iran is very hard to get numbers for, but the Muslim percentage is very high.
A recent report by a NGO in Syria has stated that in the past 4 years there have been 21,000 Christian converts. Have not seen source documentation. Syriac Christians have been in N. Syria a long time. So I’m convinced the Christian population is grossly understated in Syria.
Ok... See what you mean...