The reason is because people can't tell whether you're a Christian or Muslim, because of the features. Christian and Muslim Arabs look the same. A lot of people mistakenly think that all Arabs are Muslim so they try to avoid you. Generally, not many people want to be close to Muslims.
Coptic Christian @FCB99? Is this what you are referring to? I dated a Coptic when I was living in the New York City area and I never had a problem with this. It all depends though on what the girl is looking for in the USA. Good luck. xx