In a Nutshell:
To say “Islam means submission to one God” says little about Islam as saying "secularism is the ideology that upholds separation of church and state". While true, it does not describe how such a separation is made possible, enacted, and reenacted.
Islam is a deen, a way of life that is centered around the belief in and servitude of one God. It is often forgotten it is also a discursive tradition that is intertwined with power and politics, with the concept of dar al-Islam (the "abode of Islam") referring to the social and territorial embodiment of Islam. This means that Muslims are expected to submit to the will of Allah and live according to Islamic principles.
The first manifestation of Islam was the Prophet Muhammad's Medinah followed by the domains of the early Khulafah after him, the Umayyads, the Abbasids and the Ottomans, with Islam being dismantled in 1924 by European powers resulting in a century of absence .