.If we assume point of view that European nations are so different, then how they become so different?Had they been genetically different originally?
To answer your second question first, no. There were three sons of Noah: Shem, Japheth, and Ham. Then, of course, came the Tower of Babel. That's when the nations became culturally, linguistically, and genetically (in terms of ethnicity, not race) different. For example, a German will carry an I1b while a Pole will carry R1a; whereas a Jew descended from a German may carry I1b or any of the J haplotypes (including the Cohen Modal Haplotype)--depending on who his dad is--, and a Jew descended from a Pole may carry R1a or any of the J haplotypes. Jews descended from Khazars may carry Haplotype R1a1a1, by the way.
Meanwhile, a German will usually speak German, a Pole Polish, and a Jew Hebrew or dialect thereof (e.g., Yiddish).