All of those churches planted by the Apostles were independent of each other from everything I can find.
Not true. They worked together. Paul’s letters prove that.
All you have to do is check on the Councils held from the Council of Jerusalem onward.
The term 'church' provides a differentiation which shouldn't be there. Better translated as 'assembly' or 'congregation', or 'discipleship'... Then re-read the OT, and you will be surprised how long the 'Church' has been around.
But yes, you are right - the churches were congregational in governance... Something pretty close to how the SBA govern themselves, I would suppose.
Than you need to look closer.
The Catholic Church
Although it is not widely known in our Western world, the Catholic Church is actually a communion of Churches. According to the Constitution on the Church of the Second Vatican Council, Lumen Gentium, the Catholic Church is understood to be "a corporate body of Churches," united with the Pope of Rome, who serves as the guardian of unity (LG, no. 23). At present there are 22 Churches that comprise the Catholic Church. The new Code of Canon Law, promulgated by Pope John Paul II, uses the phrase "autonomous ritual Churches" to describe these various Churches (canon 112). Each Church has its own hierarchy, spirituality, and theological perspective. Because of the particularities of history, there is only one Western Catholic Church, while there are 21 Eastern Catholic Churches. The Western Church, known officially as the Latin Church, is the largest of the Catholic Churches. It is immediately subject to the Roman Pontiff as Patriarch of the West. The Eastern Catholic Churches are each led by a Patriarch, Major Archbishop, or Metropolitan, who governs their Church together with a synod of bishops. Through the Congregation for Oriental Churches, the Roman Pontiff works to assure the health and well-being of the Eastern Catholic Churches.