Its more complicated than that. Ideologies require expansion to survive. Once you have established Khilafah in one country, the Shariah demands to expand it to bring other Muslims into its hold. You can't just assume that the expansion would be peaceful.
When the Taliban established their government in Afghanistan and Mullah Omar was given the title of "Amir Ul Mominin", representatives of Hizb at Tahrir went to ask Mullah Omar if what he has established is a Khilafah? Mullah Omar replied, "its not Khilafat, its Emarat". A claim of Khilafat would have turned his already few friends against him which they did anyways after a while. Remember that by claiming that you established a Khilafah, you are also giving an ultimatum to the world,that sooner or later you are going to invade everyone.