As-Salaamu Alaikum Wa Rahmatullah Wa Barakaatuhu
I pray that Allah grant you success and bless us with the victory by your hands our Ameer, soon Inshallah, this matter belongs to Allah Alone, and we bear witness you are the best successor to the best predecessors
In the book: Concepts of Hizb ut Tahrir on page 73 (English version) it mentions:
"Carrying the Islamic da'wah and the political struggle for its cause can be undertaken only in the society which the party has defined as its area for activity (majal).Hizb ut-Tahrir considers the society in all the Islamic lands to be one society because its entire cause lies in one case, Islam. However it takes the Arab lands that are a part of the Islamic Lands as a starting point. It considers the establishment of an Islamic state in the Arab countries as a nucleus for the Islamic state as a natural step."