Countries come and go. I believe a national flag stains the service, as a Nazi flag would have in a German church in the 1930’s and 40’s.
I sometimes capitalize “American”, depending on how lazy I’m feeling, or whether I’m using a real computer or a phone to post. :)
For me, church is not about the country I’m in. It is about worshiping my creator among other members of His flock. I love discussing politics, even in a church building, but like to keep the purpose of the gathering pure.
Are you a Jehovah Witness???