Jhn 18:36
Jesus answered, My kingdom is not of this world: if my kingdom were of this world, then would my servants fight, that I should not be delivered to the Jews: but now is my kingdom not from hence.
To the extent that nationalism emphasizes doing things that are against our faith we must oppose it.
Nationalism comes from one's personal dedication to his/her country. I never heard that being a baptist made me an American, Canadian or any other culture. If anything, a Baptist should be British, if he believes it started with the movement in Britain..........