whether we want it to or not religions have a nationalistic tone about them, if the 19th century can be described as anything is that it is where true national consciousness begun, most nations today that have a hard time finding national consciousness today were because they didn't exist in the era. Trying to change the national religion of the time especially when it is a minority seems like a doomed premise
Is it impossible for a Japanese Christianity to be nationalist, especially if the Faith started growing in the 16th century instead of being stamped out by the Shinto-Buddhist establishment?