Adding infrastructure has a higher rate of return when there is less infrastructure to begin with. Adding one interstate highway system greatly increased US economic mobility. Adding a second would not have such benefit.
So China, not having the infrastructure the US does, likely gets a benefit on doing projects that would be a loss in the US.
This might be an overgeneralization in this case...
While generally true for developing be developed countries, are you actually familiar with China's infrastructure development practices? If one thing is for sure, it's that there isn't a shortage of bridges, trains, airplanes, and roads... The Chinese government uses infrastructure-building programs to ensure it meets its centrally-planned GDP targets and to make sure everyone has jobs. Economists are actually concerned that the infrastructure is so overbuilt that the costs of future maintenance may make the return on many new infrastructure projects negative.
Meanwhile the US is notorious for crumbling infrastructure...
>are you actually familiar with China's infrastructure development practices?
Yes, somewhat. They've poured lots of money into it over decades to catch up to the developed world. They're not likely there yet.
A simple example: they're close to the same area as the US, around 4 times the population, yet they have around 2/3 as much road miles. They make less electricity per capita than the US. They have less than half as many miles of train infrastructure than the US. If you look at all sorts of metrics for how much per capita that they have compared to the US (or any first world county), they still lag.
So if they want to get to first world levels in many of these areas, they still need to create more infrastructure.
As such, they might still get more benefit for certain infrastructure projects than the US.
>Meanwhile the US is notorious for crumbling infrastructure...
... among people in the US that complain without understanding how the rest of the world fares. In world rankings the US does very well on quality of infrastructure [1,2].
> So, the reason because the US doesn't invest in infrastructure is because the ROI is not high enough?
The reason the US doesn't invest in infrastructure is because the benefits go to everyone instead of a specific party interested enough to lobby for it.
The ROI is the much the same in the US as it is elsewhere, provided the investment is made where it's needed rather than on pork barrel projects. For example, the value of building a bridge is X, but that's also the value of maintaining/replacing it because if it collapses or has to be closed for safety reasons then you no longer have a bridge. Moreover, you can productively build things like new subway lines in cities that are growing because that's where the demand exists to justify the cost.
The lobbying problem is where we've started to see this "public private partnership" scam show up. Then you have a specific party interested enough to lobby for it, but it's because they intend to rent seek on public infrastructure by taking the public's money and then putting up a gate and charging them a second time for admission. Because $100 is a lot, but if you pay $75 in taxes and $75 in tolls then it's less, right? And if that discourages productive use of sunk cost infrastructure and is a regressive tax on the poor, let's try not think too much about that.
What about the things that China has that we don't? Like high speed rail networks? Or things we both don't have, like university that doesn't cost an arm and a leg to attend?
So China, not having the infrastructure the US does, likely gets a benefit on doing projects that would be a loss in the US.