Do you think language unites or divides us?

I believe that Language can divide people because everyone has his/her own language. For example, I was working with a group of people that  speak the same language except me, even thought we were all speaking English while we were working, but when we took a break we sat together and all of the sudden they  started speaking their own language with each other and I  felt left out and moved to different table to sit because I felt that I wasn't belong that table.  So, that is one way that can show you how language divides people.