Some churches, from years back, would have the American flag on a pole on the left of the alter while having the Papal flag similarly posted on the right. I have not seen this arrangement except in parochial schools where the Papal flag flies beneath the American flag. Flag protocol is that our national flag must be viewed first from left to right and top to bottom. However, I have not seen such an arrangement in a church is the past decade or more. There really isn't a need for it except, perhaps, on July 4th or Memorial Day.