Are Burbclaves Here Yet?

In Snow Crash, Neal Stephenson depicts a world where Hiro Protagonist's main job is as a pizza deliverer, while he freelances as a correspondant for the Central Intelligence Corporation. America's economy is at the bottom rung, commercialization is over the top, and the national government as such is impotent outside of its own district.
Although shocking, these trends, albeit in a less exaggerated form, wouldn't be unexpected. But then Stephenson shocks the reader's system, when Y. T. goes into a White Columns to deliver the pizza Hiro can't deliver because his car is submerged:
He takes her as far as the entrance to the next Burbclave, which is a White Columns. Very southern, traditional, one of the Apartheid Burbclaves. Big ornate sign above the main gate: WHITE PEOPLE ONLY. NON-CAUCASIANS MUST BE PROCESSED (32).
Here, reified on the landscape, is the sort of overt segregation that the law proclaims is past. The United States Stephenson creates seems to simultaneously regress and progress. Seems is an operative word. Neighborhoods are, by and large, still divided by race in our present United States. Sides of town are partioned, unofficially but extremely noticeably, into "black," or "white," or "Latino," or so forth. Sometimes these can take the form of "ethnic enclaves" or "ethnic neighborhoods," often concentrations of recent immigrants from a particular country or region, a label which often draws a fairly neutral, or even positive response. However, these neighborhoods can also include the poverty-created "ghettos" or "projects," mostly home to African-Americans and Latinos, sites with much more negative connotations, or overwhelmingly white country club estates or gated suburban communities, sites that often aren't considered as racial spaces.
Stephenson's Burbclaves then are not, in reality, terribly unique in conception. In fact, one could argue that they're the visual manifestation of cognitive spaces. The primary difference is that they've become the substitute for the nation state. One has "citizenship" in a burbclave, but each burbclave has multiple copies that can be found throughout the landscape, each one only marginally different from the rest. "Citizenship" earns automatic passage through the gates and hence, shelter and conviennence. Burbclaves give new meaning to the term "A man's home is his castle," as they freely discriminate to determine who can and cannot enter.
Equally intriguing is the presence of spaces exterior to the burbclaves, often the site of stores, prison franchises, and other undesirable businesses. If we follow the metaphor of burbclaves as nation-states, Stephenson has created territory outside the nations, on the peripherary between them. It suggests that some things happen outside the collected imagination of place, that real life can't spoil a constructed fantasy.
Multiple worlds collide as well. The reader sees both white supremacist New South Africa and Atazania, the black power version of the same space. One is assured that "Mr. Lee's Greater Hong Kong" is NOT the same as the real Hong Song, and Italy appears as both Nova Siciliana and Cassa Nostra. Although these places could not coincide in reality, they can coincide in the world of the imaginary.
How can we understand this comparison of gated suburban communities - or even neighborhoods generally - to nation-states in relation to stratification and division? Is there a distinction between how neighborhoods segregate and how nations do so? Should there be? Is the United States itself a burbclave?