The phrase "Working at Circuit City" is shorthand for "not able to get a career started, and so just killing time while earning a little bit of money".
For those of you not versed in the AmericanCulturalAssumption, Circuit City [was] a nationwide chain of consumer-electronics stores -- selling such things as TVs, stereos, home appliances, computers, software, telecommunications equipment, car stereos, music, and movies. Like many retail outlets in the US, Circuit City does not hire commissioned salespeople; instead they hire sales clerks at a flat wage (usually close to the minimum wage). Working there is not a desirable career; it's much like working at McDonalds (i.e., it's a McJob). It isn't a bad place for teenagers and college students to work, though, and many do.
Circuit City, Best Buy, and Fry's Electronics (and more, I'm sure) are large retail electronics (and related gear) stores in the USA. (Fry's is actually a Western USA phenomenon. They're especially infamous in SiliconValley.) These are "superstores", so, unlike RadioShack, you won't find two or three in towns of less than 100,000 people.
They sell assorted consumer electronics and appliances (though Circuit City dropped their large appliances a couple of years back). You can buy a whole bunch of consumer electronics and related gear. Of the lot, Fry's has by far the broadest range of products. It's the one thing I miss since leaving Las Vegas. Reno (at half a million people) is evidently not big enough to have one, making Sacramento (a three-hour drive away) the closest one. Fry's is actually quite different from the other stores mentioned here, as they are much more oriented toward geeks than the other stores, which are more consumer-oriented.
The people Circuit City employs are, on the whole, of the same essential demographic found at McDonalds, but the pay is marginally better, there's a more refined dress code (sort of), and they don't arrive home at night smelling of grease. Circuit City people tend to be a little older. There is an implication that they are not able to get the kind of jobs their education leads them to expect.
Customer service at such stores is often spotty; many customers know more about the products than the employees do. On the plus side, when you walk through the door at the big-box retail chains, you aren't immediately descended upon by sales vultures wearing plaid suits, desparate for commissions, who constantly are trying to get you buy something. (Many local/regional retail outlets, along with RadioShack, still use commissioned salespeople). While commissioned salespeople frequently are more knowledgeable about the products they sell (their compensation depends on it) -- the continual hounding and pressure to buy buy buy makes shopping in such establishments annoying.
For the benefit of those across the pond, Circuit City, Best Buy, and Fry's Electronics are roughly equivalent to Currys, Comet, and PC World in the UK.
Circuit City is just about out of business. They are having final sales at their stores and then will close down, leaving Best Buy as leader in consumer electronics discounting. note added later: Best Buy is closing a bunch of stores. It seems selling hardware requires competence all the way up and down the corporate hierarchy. Who knew??
Currys and PC World have merged.