Does the absence of an Islamic Caliphate constitute a sin upon Muslims, and what is incumbent upon them to do in this situation?

Muslims must unite, gather their ranks, and resolve differences to become one nation under a single banner, and appoint an Imam who meets the conditions of the Greater Imamate to establish the rituals of the religion, extend the control of the Islamic state, spread security and stability, support the oppressed, and restrain the oppressors. They must employ all legitimate means to achieve this, and those among them who are capable will be sinful if they fail to do so.