I understand that there is the excuse of ignorance for one who claims Islam concerning Shirk (polytheism) and Kufr (disbelief), so would that be the case about one who says Laa Ilaaha illAllah (there is nothing worthy of worship but Allah) and grew up being taught that Jesus is the son of God or one who says Laa Ilaaha illAllah and believes in another god besides Allah?
All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
Shaykh Ibn ‘Uthaymeen made a good distinction pertinent to the excuse of ignorance in relation to the person who commits an act of Kufr; he differentiated between the one who is Muslim and the one who was raised as a disbeliever.
“Ignorance of that which makes one a disbeliever is of two types:
The first type is when the person believes in a religion other than Islam or does not believe in anything and it never crossed his mind that there is a religion other than that which he is following. According to the Shariah, he is to be treated as he appears to be in this worldly life; as for the hereafter, his fate will be decided by Allah, the Exalted.
The second type is when the person is a Muslim but he grew up believing in (or practicing) this act of disbelief, and it never crossed his mind that it is contrary to Islam, and no one alerted him to it. Such a person is to be treated as a Muslim, and in the Hereafter his fate will be decided by Allah. That is indicated by the Quran, the Sunnah, and the statements of the scholars...”
Allah knows best.
You can search for fatwa through many choices