I think you're referring to the "midwestern palate", it's more geographic than ethnic in my experience.

I tend to think that's more of a stereotype than a reality. I mean, I've been all over this country, and the only place I've really found people to prefer bland food was in the Upper Midwest -- I may not know how it's possible to cook ground beef so it ends up with less flavor than it had starting out, but Wisconsin sure does. But that's the only place I've ever been where I could make that complaint.

Of course, now that I think about it, some of the tastiest dishes I've ever had were based around venison, and anecdotal evidence suggests that the taste of venison is rarely known among white Americans who like to go around making snide and rather ignorant comments about the tastes of other white Americans.