As I understand it, they’re only legally required to offer it in the US if the delay is caused by mechanical, staffing, or other issues in their control, but not if e.g. outgoing fights flights are grounded due to weather. They do tend to give lodging at least if you’re stuck at a layover even for weather though. But they also usually try to get out of their obligation to pay for bumping people off over booked flights by reverse auctioning with company credit.

They may also give you a voucher for some place that’s halfway across town, meaning you don’t get much useful sleep time.