What is the ruling on insulting a Muslim country; does the perpetrator sin, or does he apostatize from Islam?

If the abuser intended to abuse the Muslim residents of a country, then abusing a Muslim is considered a transgression (fisq) and not disbelief (kufr). The proof for this is the Prophet's (peace and blessings be upon him) saying: "Abusing a Muslim is a transgression."

Repentance for abusing Muslims is obligatory. This is done by ceasing the abuse, regretting what has passed, and resolving never to return to it. Abusing and cursing are not among the ethics of a Muslim, as the Prophet (peace and blessings be upon him) said: "The believer is not a slanderer, nor a curser, nor an obscene speaker, nor a foul-mouthed person." Moreover, Allah does not love the one who is obscene and vulgar.