Final answer:
Bernadou struggles with the idea of fighting for his country due to his lack of a personal connection to the nation beyond his immediate environment, which is deeply important to him.
Step-by-step explanation:
Based on the passage, the most likely reason Bernadou struggles with the idea of fighting for his country is that since his country is mainly unknown to him, he does not feel a tie to it. Bernadou's connection to his home is deeply personal and localized; he has a 'dogged devotion' to his birthplace, which is palpable and powerful to him. His patriotism is 'a narrow form of patriotism,' deeply connected to his immediate environment, which he knows and loves, rather than the broader concept of a nation, which is more abstract and thus harder for him to fight for. The passage emphasizes Bernadou's peasant status and his lack of education, suggesting these as reasons why larger patriotic ideals are less meaningful to him compared to the tangible reality of his birthplace.