Nice try, friend, but no, it hasn't. In 1 AD, Christianity barely existed even in Jerusalem. You're conflating two things- "legalization" and Christian presence, but it doesn't matter, because Europeans had both first.
Christians were in the Hellenic world and Rome before they were in Ethiopia. All the earliest Churches Christianity was introduced to Ethiopia by a Greek man, and that's why Ethiopian Christianity is clearly an offshoot of the old Greek Church. Christianity was only "legalized" in Ethiopia after 330AD.
The first Christian state was actually Armenia, another European country.
No matter how you look at it, African Christianity comes from a European tradition. Your ancestors were converted by Catholics, anyway, so all this talk of the Ethiopian Church isn't relevant to you, friend.