Islam calls to LA ILLAHA ILLALLAH (There is no deity but God)
It doesn't call to Nationalism.
Yes we have tribes and Allah, Almighty has beautifully described the reason for tribes and groups of people -
"O mankind! We created you from a single (pair) of a male and a female, and made you into nations and tribes, that ye may know each other (not that ye may despise each other). Verily the most honoured of you in the sight of God is (he who is) the most righteous of you. And God has full knowledge and is well acquainted (with all things)." [Quran 49:13]