You have to keep in mind that the average person (i'd argue, the vast majority of people) does not want to play tech support or tinker with their gear. They want toasters...you plug them in and they just work. And with that being the case, they aren't going to put in the effort to go look for a seller of said screwdriver.
From purely a marketing perspective, race/ethnicity can be useful because of exactly what you point out ... cultural differences! It's market segmentation; it's how you present your product to your target audience. But you have to know what your audience is to target your communications!
Otherwise, I'm totally with you... ethinicity, race, cultures... those lines are becoming more blurred over time. But this is a very slow process...
Chuck is back because the fans connected with the network directly AND through the major sponsor, Subway. They sent their Subway receipts to the network, made donations to the Subway's partner charity in the name of Chuck's main character, etc.
However, The Product influences The Customer. If your company (The Customer) sees more revenue from consumers (The Product) because of a direct correlation to a TV show, then they will continue to advertise with that show, that show will get funding from the network, and then the network will broadcast the show to The Product. Rinse and repeat.
To Mike's point - there are other shows out there that are making an effort to connect with fans, like the show Chuck on NBC, and their fanbase is responding in kind.
Example 1: The fanbase, via twitter and fan sites, got together on the night of the season finale, and purchased subs from Subway, dropped comment cards in the name of Chuck Bartowski (lead character) to Save Chuck. It also happened that the main character's actor, Zachary Levi, joined 400 fans at a Subway shop and made sandwhiches for everyone who came. (http://chucktv.net/2009/04/26/video-zac-plus-400-fans-go-to-subway/) You can't connect better with fans than by feeding them. ;-)
Example 2: The fanbase is streaming episodes of Chuck weekly until the new season begins. The cast sent a video thanks to the fanbase upon the 1 millionth stream.(http://chucktv.net/2009/09/11/video-chuck-cast-co-creator-say-thanks/)
The cast realizes that it was a bubble-show, and that 13 more episodes were ordered by NBC because of fans being creative and instead of only bombarding the network (a la Jericho and CBS) but also bombarding a major sponsor... and showing the major sponsor that their ad campaign is reaching the consumer. Here is a link to the announcement that the show was renewed because Subway signed on... http://chucktv.net/2009/05/19/breaking-nbc-officially-renews-chuck/