Here is a list of predominantly Muslim countries:  
"Southwest Asia: Arab nations such as Saudi Arabia, Iraq, Oman, United Arab Emirates, Kuwait, Qatar, Bahrain, Yemen, and non-Arab nations such as Azerbaijan, Turkey, Iran and Northern Cyprus. South Asia: Afghanistan, Pakistan, Bangladesh, and the Maldives. Southeast Asia: Indonesia, Brunei, Malaysia and Singapore"  Ref Google.   I would add Jordan to the list.

So if the travel ban was aimed at an ethnic group or religion, then why aren't all these countries included in the ban?  Ans:  It is determined by the U.S. government that the countries not listed do not pose a threat to national security.  Those listed pose a risk that jeopardizes the safety of all Americans.