Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
The Islamic Shariah did not set citizenship as criteria for marriage. The most appropriate quality that should be taken into account is religion, then wealth, then family relationship, then beauty.
Al-Bukhari and Muslim reported that the Prophet (Sallallahu Alaihi wa Sallam) said: "A woman is married for four things: for her wealth, her honorable lineage, her beauty and her religion, but choose the religious one you will prosper."
Therefore, if the woman whom the person wants to marry is a pious believing woman, then he has to try to convince his mother in order to marry this woman. But if his mother does not agree, then it is better for him to not marry her, as a sign of respect and kindness to his mother, because if someone leaves something for the sake of Allah, Allah will compensate him with something better.
As regards the wish of his mother to marry him with a woman he does not want to marry, he is not obliged to obey her in this matter.
Sheikh al Islam Ibn Taymiyah Said: "The parents have no right to oblige their son to marry a woman he does not wish to marry."
This man has even more right to refuse the woman he does not wish to marry if she is not a practicing, pious Muslimah.
Allah knows best.