Where does Jesus command Christians to go to church on Sunday?
Not everything Jesus taught ended up in the Bible. Catholics and Orthodox also have the Apostolic Tradition, and that's where the command is.
source
Why an empty cross in your church?
Personally I do not have a cross of any sort on my church nor an empty tomb. Jesus is no longer on the cross so why should I want to keep Him there. The amount of time that He was there was more than sufficient for all.
source
Why the churches are ever breaking up?
The denominations of Christianity is a natural thing due to the human fallen nature, probably also to the secret will of God. The Scripture requires interpretations, and interpretations produce a variety of understandings. As a result some people leave the church and start their own. Denominations itself is not necessarily a bad thing, God still can use each of denominations strength and advantage to accomplish certain purposes.
The early church had many problems as well, its own model is no longer suitable to the contemporary need. Some of the Paul letters primarily deal with the problem in the churches. When human civilizations change, the church should be flexible in confronting the challenges from the world and seek the best way reach them, meanwhile keep the sounds doctrine.
The Roman Catholic church is consistent in keeping church in unity. But protestants continously become dividing and individualistic. The establishment of Christian Church as a part of national organization during Emperor Constantine was a necessary step for the formation of Christendom which would be able to defend the invasion of Muslim outside of Europe in the coming millennium, so that Christians could spread its message under the political and military protection. Although, the will of GOD done anyway, but its sovereignty in history never lost.
source
Time to Separate Church and State?
The same very people that frowed upon religious studies and prayers in the school are the same very ones that wants to "backraise" God. We have neglected our religious education, but are quite happy to spend time and money with psycholigists and quack pastors.
source
Does the American flag belong in church?
I've never been to a church that prominently displayed a flag, some of them had flags outside on a flag poll but not inside or anything. I think that a flag would be a bit out of place in most churches, then again I'm not exactly much of a church goer.
source