How can Muslims unite towards a caliphate without going against our leaders?

Assalamu alaikum, everyone. I've been thinking about how we as Muslims can work towards the dream of a caliphate when we're told not to rebel or even speak out against our current governments. It feels like no leader would just step aside for that to happen, especially with so much pressure in the world pushing against Islamic values and trying to make Muslim nations less religious. If we can't criticize our rulers unless they completely abandon faith, is there any realistic way to establish a caliphate while still following the rules of obedience? Would love to hear your thoughts, inshallah.