Does Islam considers all the muslims all over the world as a single nation or does it acknowledges different nations based on region or ethnicity? I am not talking of "ummah"
Islam completed when when all the Muslims were in Arabia, hence were a single nation, later other nations were conquered by the sahabas to unite them with the single Islamic nation and prophet explicitly equated non Islamic nationalism to Jahiliyah.Prophet pbuh had explicitly ordered against this phenomenon called as asabiyyah(Nationalism\casteism) , which means fighting for ones own tribe, caste,party or nation and according to Islam any fighting should only be for the sake of Allah and his deen and not for a piece of land,a caste, or a nation .Hence Islam completely rejects the concept of Nationalism and the existence of different nations other then the single united Islamic nation as evident from following hadith:
You are all the children of Adam and Adam was made of clay. People should give up their pride in nations because that is a coal from the coals of Hell-fire. If they do not give this up Allah (swt) will consider them lower than the lowly worm which pushes itself through Khara (dung)." [Abu Dawud and Tirmidhi]
It is narrated that, Rasulullah (sal Allahu alaihi wa sallam) said: “He is Not one of us who calls for asabiyyah, (tribalism/nationalism) or who fights for asabiyyah, or who dies for asabiyyah.” [Abu Dawud]
The Prophet sallallaahu ‘alayhi wa sallam said:“Whosoever leaves off obedience and separates from the Jamaa’ah and dies, he dies a death of jaahiliyyah. Whoever fights under the banner of the blind, becoming angry for ‘asabiyyah (partisanship and party spirit), or calling to ‘asabiyyah, or assisting ‘asabiyyah, then dies, he dies a death of jaahiliyyah." [Sahih Muslim (6/21)]
I guess you are wrong somehow. In Islam; Quran muslims are called the people of the last time. We believe that Holy Prophet is the last Messenger of Allah, that is why muslims are the people who are the last ones. Other prophets and their people came a time before us and are thus called previous one. There is no other term (according to my knowledge), some Hafiz would share an ayat (verse) from Quran for this.
Islam doesnot distinguish people belonging to religous groups, but it does distinguish people based on geography and history and this is supposed to just distinguish their behaviour toward Islam.