Re: If the Imam Mahdi (pbuh) came as a non-Arab, will most Muslims reject him?
As for rejecting Mehdi (AS), that is out of question, because his acceptance would be will of Allah, as it would be Allah that would give him strength, recognition, and acceptance. And whatever Allah wills happen.
Anyhow, as far as Mehdi (AS) getting born as person with no Arab connection, then, that is not possible though it is possible that he is born as non-Arab but with Arab connection, as descendant of Prophet (SAW).
We have to understand that, in Islamic belief, blood line does matter. Person’s soul was created before human reached this earthly world. Since time of Adam (AS), each human soul is getting transferred generation after generation, to person from whose line that soul is to be born.
For instance, soul of Prophet (SAW) was associated with Adam (AS), through whose linage got associated with Ibrahim (AS), and then amongst children of Ibrahim (AS), got associated with Ismael (AS), and kept getting associated until time Prophet (SAW) soul got associated to prophet (SAW)'s father Abdullah (AS) and from him Prophet (SAW) was born.
We also have to understand that a pious soul of descendant protects the person carrying the soul from major sin or shirk (in their beliefs). That means, all who was carrying the soul of Prophet (SAW) in their linage were free from major sins and shirk.
Same way, soul of Mehdi (AS) was there in the linage of Ali (RA), and through him descended to the children of Hz Fatima (AS) and carried forward until he would be born (or is already born). That means, Mehdi (AS) would be descendant of Prophet (SAW) regardless of where he would be born ... be from those who are considered Arab today, or from those who are considered non-Arab but have Arabic background (would be descendant of Prophet (SAW) who migrated out of land considered Arab today).
[Note: Descendants of prophet (SAW) faced persecution in Arab controlled world through out early days of Islam (Ummayads and early Abbasi period), and thus, many migrated to areas outside Arab controlled world, where they could live peacefully. Thus, one would find Syeds in huge number living in non Arab world, especially in India, Pakistan, Iran, Afghanistan, and Central Asia, that was controlled by early Muslims but was away from direct Arab control. Today, descendant of Prophet (SAW) are also living in many western world.
That means, If Mehdi (AS) is not born yet, than his birth could be anywhere, as he would be descendant of Prophet (SAW), and presently, descendant of Prophet (SAW) are living at many places outside Arab world]
As for what Allah decides, that happens, and it is decision of Allah that Mehdi (AS) would be born as descendant of Prophet (SAW). So there could be no change and Mehdi (AS) would be born as descendant of Prophet (SAW). We learned about Allah’s decision through the words of Prophet (SAW).
Actually, control over world events and knowledge of Allah is so absolute, that changes never happen … and if anyone thinks that such change could happen due to any need, situation, or circumstances, regardless of what Allah has already decided, than that person with such beliefs shows doubt about Allah's control over worldly events and knowledge of Allah (and that is kufr).
Thank you very much for the great, detailed explanation. The reason for my question was that I do not believe that the middle east is the center of the world or even of that great importance. The middle east is not even the center of the world's Muslim population any more, this is more in Pakistan/India/Bangladesh/Indonesia. Hence I really don't see any reason for the Imam Mahdi(pbuh) to be born as an Arab in the middle east (I don't believe he will be born Chinese either - that was just an outlandish example). I am glad to know that being a full Arab is not necessary, just being a descendant is enough. I am sure there are Syeds even in the USA., so the Imam could appear almost anywhere in the world.
As for his acceptance by people - I am sure he will be successful ultimately, but not without some struggle amongst people (especially with the Dajjal coming too). Also if he is born in India, there will be difficult of his acceptance in Pakistan and vice versa.
I did not mean to imply that Allah does not have complete control over events, but we also do not know exactly how his wisdom works. We can not question what he will decide to do at any time.
BTW. though I am a Hindu, I think Islamic prophesies regarding these matters are the most accurate because they are the latest (in historical terms) - you can see the future clearer when you get closer to it.