Are we actually doing our jobs?

As Christians we should be the hands and feet of Christ spreading the gospel message to the corners of the Earth. In recent months I have come to many cross roads in my life, like more humans come to christian or non-christian; whether it be career choices, relationships, faith, and Church.
My issue is with the word Denomination. Denomination is a religious group that includes local churches often times larger then a sect. So under the umbrella of the Christian religion we have several sects or denominations such as; Baptist, Lutheran, Methodist, Pentecostal ect. ect. Each denomination shares a connection to the Christian religion through various pipelines.
My struggle has come the fact that we supposed to be the hands and feet of Christ we as Christians are the church body, we are suppose to work as one body, in perfect harmony to lift the name of CHRIST HIGH! But how do we do this? Take a look in the city in which you live in, you will see several churches of different denominations of the Christian religion scattered throughout the city or maybe there maybe three churches right in a row, just drawing a different crowd every Sunday.
My problem and something I just can't wrap my head around are the 'three churches sitting in a row' these three churches like in most cities probably have very little to do with each other outside of the fact the probably worship Jesus. Why when three churches sit right in a row, are they not actively working as one to reach their lost city? Why can, or why do denominations hinder the church more then help, why on any given sunday those three churches in a row will not speak share or even try to organize a group to work together to advance the kingdom of heaven. Why do we feel we can only do that within our set denominations? Why don't we hear of a Baptist, Lutheran church working together by setting aside some of their petty arguments or disagreements and focus on what we are all sent here to do?
This question has weighed my heart down for months, how can I figure out a way to some how show the churches in my community it is alright to work together? Why can't we do what Christ asked and stop trying lift ourselves up or our churches and lift HIS NAME UP?
When we stop relying on a Denomination and start relying on God and our work with our other Brothers and Sisters in Christ. When will man stop getting involved in Gods' plan and putting his own twist on it?

Thoughts?