If, as you have mentioned in your YouTube presentation, deen doesn’t deal with complete political system, then why at the time of Prophet (pbuh) and the four caliphs, battles and wars were engaged to occupy the other lands apart from Makkah and Madina, of course, after making sure that the work on strengthening the faith of the companions was complete. If dominance of Islam was not important, then why did all wars take place, they could have continued preaching Islam, rather than occupying the lands.
It is important that we understand all significant aspects of Islam from Qur’an. The battles fought by the prophet, alaihissalaam, were a punishment of God for the disbelievers because of the fact that, like all other Rasul, the prophet had done itmame hujjah (conclusive presentation of God’s message) on his immediate addressees and they persisted in denying God’s message. That’s why the Qur’an says about these wars: “Fight them so that God may punish them at your hands” (9:14); and “It was not you who killed them, but God did so …” (8:17).Read carefully verses 1 to 11 of Surah Muhammad (47) to understand what I am saying.
If the same thing is to be done by the later-day Muslims, who is going to decide who were the disbelievers who deserved to be punished and who were the people who had reached the level of purity that they were going to be helped by God? It is because of this reason that the later-day Muslims can only undertake Jihad for either defense or to undo fitnah (religious persecution). Moreover, Jihad can only be undertaken by an Islamic state and not by small groups of Muslims who if they were going to take up arms would cause another fitnah.
Your question is a good example of what I have tried to identify in the YouTube video: By declaring Islam as a complete code of life, many Muslims start doing things which were only meant for the prophet and his companions to do and as a result cause great harm to the image of Islam.