ANSWER:

It’s not permissible to wear it or possess it but it’s not shirk!

Me and my family got football shirts as gifts from the AC Milan team. I can’t remember if we realized it back then, but now I’ve thought about it and noticed that there’s also a Christian cross on it, which is striking. I googled it and it really is a Christian cross. Is it a sin that we carried it outside? Or also Shirk?