Assalamu alikum it is mentioned in Sahih al Bukhari Narrated Ibn `Umar: When these two towns (Basra and Kufa) were captured, the people went to `Umar and said, "O the Chief of the faithful believers! The Prophet (peace be upon him) fixed Qarn as the Miqat for the people of Najd, it is beyond our way and it is difficult for us to pass through it." He said, "Take as your Miqat a place situated opposite to Qarn on your usual way. So, he fixed Dhatu-Irq (as their Miqat)." Reference : Sahih al-Bukhari 1531 so does that mean people of Iraq considered themselves najdis? that is why they took the verdicts of "najd" on themselves.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and messenger.

Iraq is not part of Najd. The people of Iraq did not consider themselves the same as the people of Najd concerning Meeqaat. Rather, they just meant that this spot, which was the closest to them from among the Mawaaqeet (plural of Meeqaat) which the Prophet, sallallaahu ‘alayhi wa sallam, designated, was located distantly sideways from their way, and they found hardship in reaching it. Therefore, ‘Umar ordered them to assume Ihraam near Qarn, which is Thaat ‘Irq.

Indeed, there are Hadeeths that were reported which indicate that the Prophet assigned Thaat ‘Irq for the people of Iraq to assume Ihraam from and then the scholars differed in this matter. More than one of the competent researching scholars stated that this Meeqaat was designated by the Prophet himself and that the designation of the same Meeqaat (for the people of Iraq) by ‘Umar was in conformity with the text of the Prophet and this was not the first time in which his opinion was in agreement with the Prophet's statement.

Al-‘Ayni said: "I said: The Hanafi and Hanbali scholars as well as the majority of the Shaafi'i scholars, and Ar-Raafi`i in Ash-Sharh Al-Kabeer, and An-Nawawi in Sharh al-Muhaththab, stated that this Meeqaat was designated based on a Prophetic pronouncement.” [End of quote]

Allaah Knows best.