On a legal basis I’m not sure, but on a theological basis many people find it very important to separate patriotism and allegiance to a particular government from theological beliefs, which is why many saw Trump’s Bible as heretical.

It’s also worth pointing out that rejecting state influence over religion is the original reason for the concept of separation of church and state, at least in America. It was was far from the norm at the time.

[1] https://firstamendment.mtsu.edu/article/establishment-clause...

[2] https://goodfaithmedia.org/heresy-of-the-trump-bible/