Religious laws deal only with Muslims and no scholar ever said that the religious law of shariah can be applied to the non-Muslims too. So even if Islam is adopted as a state religion, it will not be applied to non-Muslims.
Public law has to be secular in nature, no other foundation can be adopted for it, except that a community demands to use its religious law in their public matters too and it may not affect the other party when involved.
Secondly, nation-states are not created by Muslims. They were imposed by the world order. A nation can deny accepting it, but it has to declare it first and then face the consequences too. It is not fair to claim to be a nation-state and a religious state at the same time. Since the state is not acquired by the Muslims only, and it was created on the principle of the nation-state, therefore legally and ethically Muslims have no greater claim on its ownership than that of non-Musims. If some country is conquered by the Muslims only, as is the case with the Taliban in Afghanistan, it is their right to impose their agenda.