The shred of policy substance in last night's conservative "discovery" of a 2007 public speech that Barack Obama delivered in New Hampshire and was covered at the time (see Dave Weigel for a full account of the conservative race-baiting on this) was Barack Obama's statement that "we don't need to build more highways out in the suburbs."
Obama was completely correct about this, and it's unfortunate that as he's shifted from an early-stage primary candidate to an incumbent president he's largely abandoned the point.
There may be a some well-justified suburban arterial projects in the United States, but generally speaking this is a terrible use of federal money when what we should be focused on is better management of existing infrastructure. The basic model of suburbanization says that people balance land prices against commute times. If you move further from an employment center you can get a cheaper or bigger place ("drive till you qualify") but you pay that back in financial (gasoline) and time costs of commuting. Adding to the metro area's roadway capacity serves in the first instance to decrease congestion, speeding commuting times. But with commuting times sped up, the cost-benefit analysis switches and you get new development further out until the road is re-congested and you reach equilibrium again.
Does that mean you can never build an uncongested road? No. Rather, the issue is that taking up space on a road imposes a congestion externality on others. As long as that externality is unpriced, you're either going to have overconsumption of road space (traffic jams) or else massive overbuilding (bridges to nowhere).
Either way, rather than spend money on new arterials what you want to do is make money by pricing congestion properly. In some cities, spending that money on new rail transit capacity would be a good idea, while in other places it would make more sense to just hand it to poor people directly to offset the regressive fiscal impact. Now none of that is to say that if there's a jurisdiction that wants to take a rural area and build roads to attract suburban development that the federal government needs to stop them. But there's no particular reason that encouraging this should be a federal priority.
Meanwhile on a local level a lot of jurisdictions should be looking hard at freeway removal. Many urban freeways (East Coast examples include I-83 and the 395 spur in Baltimore, the Southeast/Southwest freeway in D.C., the Vine Street Expressway in Philadelphia, most of the highways in the Bronx, the Oak Street Connector in New Haven) constitute cities using public land to subsidize living far from the city center while offering little net transportation benefits to city residents. Some urban freeways (like I-95 in Philadelphia) constitute unfortunate decisions to local key parts of the national road network in the middle of dense urban areas, but a lot of them are "spurs" and "connectors" of various kinds with no non-local significance and a negative impact on the cities that host them.
It's a bit unfortunate that in their zeal to demonstrate that "you didn't build that," a lot of progressives have lost sight of the fact that many of the things the federal government helps build probably shouldn't have been built.