The most obvious way to see this was during the government shutdown, when the House Republicans only had to sell their anti-government posture and their budget stonewalling to disproportionately conservative voters within their own distinct country. But the effects of this separation are also felt on other specific issues.

With this in mind, we spent the last few weeks digging through Census data on congressional districts to get a CIA World Factbook-style portrait of the two countries in the House—the one within all the GOP districts (Republistan) and the one within all the Democratic districts (Democravia). The full results are in a table at the bottom of this post.

We did this with a very simple question in mind: How do the differences between the two nations represented in the House correspond to the larger policy differences between the parties?

For starters, take the recent food-stamp cuts championed by House Republicans and opposed by House Democrats. The House GOP represents a country where only about 12 percent of residents receive those benefits, while the House Democrats represent a country where more than 15 percent of residents receive those benefits. That gap does not fully explain the parties' differences over food stamps. But with Republistan less financially reliant on food stamps than Democravia, it may exacerbate those differences.

The periodic battles over federal funding for public-transit systems provide another example. To an America where 5 percent of all residents—or more than 15 million people—rely on public transportation to commute to work every single day, proposals to cut those resources can seem misguided. Such initiatives must seem even more destructive to a House Democratic Caucus that represents a country where almost 9 percent of residents use public transportation to get to their jobs. But in the separate country House Republicans represent, only 1.4 percent of residents use public transportation. That means almost 13 million of those 15 million people who rely on public transportation live in House Democratic districts. Consequently, House Democrats defend such funding while House Republicans push not merely to reduce such funding—but to entirely eliminate it.

The same political dynamic could shape the upcoming debate over tax reform. A full 69 percent of housing in Republistan is owner-occupied, but owners only live in 58 percent of the housing in Democravia. With Republistan having a much larger population, it probably has tens of millions more people than Democravia who potentially benefit from the home-mortgage interest deduction. Not surprisingly, House Republicans have been more skeptical of proposals to limit the deduction, while Democrats have seemed more open to the idea.

Of course, district-by-district Census data show that no demographic difference between the House's two countries is more severe than the racial divide. While it isn't news that GOP districts tend to be whiter than Democratic districts, how much whiter is notable.