I don't know about it being a "white people thing", but I can tell you one thing for sure, it is an "American thing".
I have traveled all over the world extensively and you would not believe the "nostril cheddar" that folks in other countries give off. I am not talking about the usual culprits like Hispanics, ME or African territories either. The French can be down right hideous at times. Italians? Well, they didn't popularize the phrase "Italian bath" for nothing. British? "The paler the wench, the stronger the stench".
Americans
Canadians
Swedish/Germans
Top three right there for not giving you an olfaction assault. Though in most cases, it doesn't take those kinds of people long once they get here in the States freshen up a bit. Unlike their countries where everyone around them ignores them and pays their reeky ass no mind (probably because they smell just as bad themselves) over here people will speak up about it or at the least make it obvious they are moving to get away from them.