This was the question raised by Dave Mann recently at a gathering of churches when talking about unity. When Jesus talked about the vine, I don't believe He was limiting it to the sphere of each congregation. Rather, Jesus had His universal church in mind.
In other words, we need each other. Instead of church life being largely insular, what if we really understood what Jesus was getting at? That, while we may worship individually, in our own unique ways as churches, that our faith expression together as "the church" is what Jesus was hoping for in John 17.
There is a word I have been mulling over...synergy. That is the interaction of two or more forces where their combined effect is greater than the sum of their individual efforts. In Ecclesiastes 4 it talks about this, two being better than one. This is how we were created to be, man and woman coming together in unity.
Two are better than one...for if they fall, one will lift up his fellow...Again, if two lie together, they keep warm, but how can one keep warm? Ecc 4:9-12
Jesus sent His disciples out two by two. Paul had Epaphroditus, his companion in labour, fellow-worker or sunergos, describing a synergy of labouring together. Moses had the support of Aaron. There is a story of a horse-pulling competition, where horse 1 pulled 5000lbs and horse 2 pulled 4000lbs. They put them together to see what would happen, and to their surprise the horses combined pulled 12,000lbs! Together there was far greater combined effect.
'What could we do better together?'