If you live the Sermon on the Mount you cannot perform as a member of the military. Do you know that if you do not live the Sermon, you do not have Christ according to John?
I would think if being in the military hindered the believer, there would be a specific illustration of that displayed in the Scriptures. However, God reached the life of both the centurion in the prison and the one who accompanied him in shipwreck, as well as “those in Caesar’s household.”
Although my citizenship is in the Kingdom of the King of kings, I do not have a particular problem with a certain level of allegiance to the rulers in which I am to pray and the constitution under which I live.
Citizenship does have advantages. Was it not used by Paul to minister to those in Rome?
However, should the government decide to discard the constitution, and Texans rise to secede, then just as R.E. Lee and T. Jackson, I will follow where I reside and trust the providence of God.