It's... complicated.
A big problem IMO is the politicization of funding.
So for example, when doing road maintenance, it's unique in that it is essentially ALWAYS cheaper to do the maintenance NOW rather than later. So like doing a cheap slurry seal/ chip seal on a road that was just paved 2 years ago is probably actually a really good idea. If you do maintenance like that, you can pretty much maintain that road indefinitely at remarkably low costs. As roads degrade toward failure, the costs to repair them go up exponentially. However, the public doesn't get it. They see the road that is already failed, full of pot holes and cracks and wonder why they're spending money fixing a road where nothing is wrong instead of doing the same thing to the failed road. What they don't realize is that the cost to repair the failed road is 10x, 25x maybe even 100x more expensive than that cheap slurry seal. But they can't differentiate between a seal, or an asphalt overlay or a full repair of the road and subgrade. So the optics of correct and optimal road maintenance strategy are weird, and make the road works strategy dependent on political whims.
Now the problems really start to compound. Politicians in the US have been divorced from the reality of costs for a long time. Local jurisdictions essentially rely on "emergency funding" to do the really expensive (over 10-100x cost) repairs that could have been entirely avoided if they had just spent the money to do the maintenance earlier. But they had basically NO incentive to do so. If anything, to get the big money from the state or the fed, they have to let it fail so that it looks really bad and becomes a genuine priority or safety issue.
They also just can't help but spend the money on feel-good sexy-looking bullshit out of the general fund instead of properly funding the boring infrastructure projects, because, like a good IT guy, no one notices at all when you're doing your job well.
Couple that with polarized politics: Republicans can't help themselves but fight to cut taxes that should go to things like this because they are displeased with government waste and Democrats can't help but spend the tax revenue on other things without worrying about how to pay for them all until tomorrow. So the end result from both sides is: There's just not enough money to do things the cheap way, so now there's REALLY not enough money.