Federal highway dollars get dropped in to build, but then no dollars are available to maintain.
https://www.strongtowns.org/journal/2017/1/2/five-ways-feder...
They could subsidize the infrastructure required to integrate the country and keep the non-dense areas viable even if these areas don't have the local tax base to pay for that infrastructure, just as they did with federal highway dollars when they were built, just as many other countries are doing. It's a choice to do so or not. The rules of who pays for maintenance of which parts of infrastructure are essentially arbitrary and the U.S. can alter them if they choose to.
Other countries subsidize rural areas primarily for 3 reasons: 1. Certain political parties have their base in rural areas and want to subsidize their life style. 2. Strategie for making the country more food-independant through farming. 3. Military strategie for having people in remote areas.
Nobody in the world subsidizes non-productive suburban sprawl.
The suburbs are politically very important in the U.S. because a lot of people live there. The question of most national elections is whether the suburbs will ally with the urban core or the rural areas, and the answer is usually the rural areas.
It's like saying a poor person CAN afford a new iPhone if they just only start eating only rice and beans, and therefore iPhones are affordable for the poor. It's not just about whether the cost can fit the budget, but about what you're getting for that cost.
In my state (New York), US and state designated highways are maintained by the state if it isn't located in an incorporated city. So my city (Albany) can barely afford trucks to plow the snow, but you literally cross the city line and an army of DOT trucks are plowing. Long Island is a great example of this, as "towns" with 300k people aren't incorporated, so they get "free" services.
Even sewers are the same story. It's way more expensive to maintain buried infrastructure in the city and very cheap in the burbs. Fewer connections == fewer excavations == less labor.
If the State pays for services in unincorporated areas, it should still pay for those services in incorporated areas. The only difference should be in management - that the State manages the budget for unincorporated areas, but the municipalities manage the budget for incorporated areas.
If municipalities are expected though to raise their own taxes to pay for these services, then the tax base can't afford it, because they're already paying to maintain the rural infrastructure through the higher State taxes.
First up, you seem to be conflating the source of infrastructures funding (state vs city) in an area with whether the population of that area could without external funding pay for their infrastructure.
And secondly, while maintaining buried infrastructure in the city is likely more expensive, your argument presents no claim that it is more expensive _per capita_.
edit: see http://usa.streetsblog.org/wp-content/uploads/sites/5/2015/0... for some numbers on the last point
In my city, a tax/ratepayer base of 100,000 people bear the burden of supporting hundreds of miles of streets and other infrastructure. Guess what? They cannot afford it.
1 mile away, most of those costs are supported by 20 million state taxpayers.
This is precisely the same as the problem with schools. My City School District is struggling to get funding to cover basic services because they have to deal with a larger, poorer and sicker student body. That district one mile away is debating whether or not they should have a full size Olympic swimming pool or not. No poor folk, fewer disabled kids who need expensive intervention and a larger tax base.
https://en.wikipedia.org/wiki/Fuel_taxes_in_the_United_State...
https://taxfoundation.org/gasoline-taxes-and-user-fees-pay-o...
- Land use. While every transportation mode uses land, cars use way more, and in dense urban areas that land is very valuable; users of the land who are driving are getting it 'for free', when it could go to a more productive purpose.
- Pollution
- Noise
- Danger
All of these are 'costs' that just looking at how much money you spend on roads won't account for.