What is the ruling on one who prevents a woman from wearing the hijab, is content with her immodesty, and claims that the hijab is alien to the national culture in a Muslim country?

If the claimant's intent behind stating that the hijab (definition) is alien to the national culture is to deny its obligatoriness, then this is a rejection of the texts that establish its obligatoriness, and it is considered major disbelief (kufr akbar) that expels one from the faith. He must repent and be taught the relevant texts. However, if his intent is that the hijab was not part of his country's culture before Islam, then this is true; for Islam came with laws, including the hijab, which contain goodness, and it abolished every custom that contradicted them.