Societies where men have larger dicks are due to a biological arms race stemming from the promiscuity of their women:
>Women thirsty for cock
>Beef becomes increasingly roasted and loose
>Seeks larger cock to satisfy themselves
>Men with larger cocks sire more children and pass down their large cock genes
>Men in said society will increasingly have larger cocks and their women increasingly thirsty for larger cocks

Let's look at the evidence from smallest to largest

Indians: Arranged Marriage Tier
Asians: Faithful Docile and Tight Tier
Whites: Would Fuck a Dog Tier
Blacks: Twerking Feral Ape Tier

Any disputes?