Well, the native Arabs and Assyrians are Semitic in those 2 countries.
Genetically around half of all Iranians and Turks (Anatolians) are Semitic in origin as confirmed by DNA. Both of them have been Arabized to a large extend anyway.
In the case of Anatolians they have just been Turkified and in the case of Iranians (who are all mostly natives) they adopted an Indo-Iranian language due to small invasions of Central Asian nomads from Andronovo in modern-day Kazakhstan. For instance the oldest civilization found in Iran were the Elamites next door to Iraq and Eastern Arabia. They did not speak an Indo-Iranian language but a language more closely related to Semitic. Their culture too was closely related. In fact they are grouped alongside Mesopotamian civilizations and were mostly based in Al-Ahwaz which is geographically tied to Mesopotamia.
Only in the Arab world (in the region) do you find civilizations and peoples who have remained true to their origins throughout. That is why fellow Semitic peoples and Afro-Asiatic peoples were this quickly "Arabized" and prior to that "Aramaicized". It was a natural and internal process rather than outside invasions from foreigners.
@Arsalan have you seen my PM's to you? Send them a few minutes ago. Kindly take a look.