The first reason there are divisions in the church is because of the immaturity of many believers. Paul wrote, 'And I, brethren, could not speak to you as to spiritual people but as to carnal, as to babes in Christ. I fed you with milk and not with solid food; for until now you were not able to receive it, and even now you are still not able; for you are still carnal. For where there are envy, strife, and divisions among you, are you not carnal and behaving like mere men?' The next reason is because there is a devil who works relentlessly to divide brethren over doctrinal issues. Paul wrote in 1 Timothy 4:1, 'Now the Spirit expressly says that in latter times some will depart from the faith, giving heed to deceiving spirits and doctrines of demons.' Another reason is that sometimes men draw disciples after themselves rather than making disciples of Jesus Christ (see Acts 20:28-30).
You asked if the church is in danger. Sure, but keep in mind that there have been divisions among believers from the beginning. The real question is, what is the true faith? What must we believe to be part of the true church of Jesus Christ? Jesus is coming for a glorious church in which there are no divisions. It will be one unified body.