How can 2 churches of the same denomination be COMPLETELY DIFFERENT?

It's due to a difference in local community cultures. The predominant culture in any given area has always shaped the religion practiced there. The simple fact is that if people can't relate to a church and the way it's clergy does things, then that church isn't going to last very long. That's the reason why no single type of church can ever really satisfy everybody everywhere, and there will always be different denominations, different Biblical interpretations, and different liturgical customs even within the same sect.