The church building is a building set apart for the express purpose of worshipping God. The building is consecrated by the bishop as a place where the whole family is welcome to gather to celebrate the Sacraments (Baptism, Reconcilliation, Eucharist, Confirmation, Holy Orders, Weddings) and other services worshipping and praising the Lord. It is a central place for the parish, and, when the Sacraments are celebrated, all are welcome to attend.
Yes, God is present everywhere, and we can pray and celebrate His presence and His love anywhere in creation - it is all His. But, the church building is designed and set aside for this purpose, and is known to all to be the place where the Sacraments are celebrated.
I see that the validity and licitness of your baptism was called into question here. As bellesjoy pointed out, your baptism was not in the Catholic church, and, as such did not need to meet the requirements for the Catholic celebration, but those of your own church. **
If** you are seeking to enter the Catholic church, then we would look at your denomination to determine if it was valid within your own denomination and if your denomination intended the same by baptism that we do and that the form of your baptism is considered as a valid baptism by the church. The place that you were baptized would not have bearing unless it made your baptism invalid within your own church.
Valid baptism, as with all of the Sacraments, can occur anywhere. The norm, the preferred celebration, is in the church, the place set aside for worship and celebration, consecrated to that purpose, and performed by/with the ordinary minister of the Sacrament, a priest or deacon (depending on the Sacrament), open to all of God’s family.
Does that answer your question?