I'm regularly astounded about how the U.S. has so much money in general, but can/won't invest in betterment of its citizens (current and future) because it's either self serving or in a state of decline.

The money is there, we have the largest federal budget on the planet. It’s just tied up in endless wars, incarcerations, and pork barrel projects. And those things individually aren’t necessarily bad but we do it with such largesse it leaves very little room for anything else. The way our politics work is no one can plan multi decade projects if you can’t do it in one term then don’t bother.

For the MTA specifically it isn't a matter of money. They are so insanely inefficient and poorly run that the entire NY + NYC budget wouldn't be enough without serious reform.

The US is terrible about infrastructure maintenance. I think it's a combination of two things: Firstly nobody gets their picture taken cutting a ribbon for a maintenance project, and secondly if infrastructure is crappy then nobody wants to pay more taxes because obviously the government doesn't know how to take care of things. It's a double whammy of failure.