I'm not USian either.

There is no sense in allowing a private profit from a natural monopoly with no risk attached (we're never going to decide we can live without clean water and water is supplied geographically, you don't get to choose the provider). Demand will always be there and, as a society, we are much better off doing all the work you describe at cost. Lining the pockets of shareholders does not make any sense. But that is exactly what is happening.

I'm in the UK. It is an extremely sore point here: Water firms’ debts since privatisation hit £54bn as Ofwat refuses to impose limits

Ofwat is refusing to limit the soaring debts run up by water companies as research reveals the firms have outstanding borrowing of almost £54bn accrued since privatisation.

Customers are paying on average £80 or 20% of their water bill towards servicing debt and rewarding shareholders, according to the Competition and Markets Authority (CMA).

The scale of debt, or gearing, taken on by the nine main water and sewerage companies in England is raising concerns about their financial stability as interest rates rise.

The level of net debt held by water companies is revealed as Guardian data shows the main water and sewerage firms in England have paid dividends to shareholders of £65.9bn up to 2022.

Note the £54bn in debt they're charging us 20% to cover (first para) compared to the £65.9bn they've doled out to idle shareholders (last para), mostly via tax havens, just to add insult to injury.

And the sewage they are spilling into our waterways because they have not invested in infrastructure. Why would they when they can hand the money to shareholders and rely on the govt not to make them meet even the most minimal of standards?

People are not stupid. There are overwhelming majorities in the UK for nationalising water (and rail, mail, energy, all the stuff that it makes no sense to privatise). But democracy does not mean shit when there's profit to be extracted. And the profiteers do their very best to make us stupid by insisting there is no other way and wearing everyone down until they believe it. Which is easy, because they own all the media so even if we don't entirely buy their bullshit, it's very hard to hear anything else above the din they're making.