They either should have put the people on other airlines and paid the bill like a normal airline, or run a flight in the middle of the night like Delta often does and pick them up at 4am thereby not significantly disrupting the day time schedule.
This is the kind of experience that invites government mandates. Apart from standard duty of care (meals, phone calls, and a hotel room) I can outline three options from Wash DC:
1. The carrier sends one of its planes there to depart within 24 hours
2. The carrier can charter an aircraft to depart within 24 hours
3. The carrier can book passengers over to other scheduled carriers, paying up to full published (J, Y) fares, with departures within 24 hours
Carriers that fail to do that pay a significant fine, on the order of 3x the cost of walk-up fares. Carriers that fail twice to do that within one year get their license to fly yanked. They will find adequate staff and aircraft to rebook passengers under those conditions. You'll need to find your own way home
is not an acceptable treatment of U.S. passengers.
Minnesota SY passengers, write to your Congressman.
This proposal is far too simplistic, and as a result airline lobbyists would find it all too easy to stall it in Congress, and even if by some miracle it passed, airline lawyers would find it all to easy to argue in court that in some circumstances it is impossible to comply with, and so get the law struck down.
First of all, when does the 24 hours start from? The original scheduled departure time, or the end of the severe weather event - and severe weather events can last for several days? Who would define for legal purposes when the severe weather event ended? We've had in the very recent past situations where Caribbean airports were rendered unusable for days or weeks by hurricane damage, and the actual hurricane affected the area for more than 24 hours!
Then, if you had resolved that issue, sending one of an airline's own fleet or a chartered plane within 24 hours might be possible for Mexico to Minneapolis, but what about say Morocco to Minneapolis, should such a service start in future? You get into issues about flight duration, places being in radically different time zones, FAA crew hours regulations, lack of planes with appropriate ETOPS certification and clearance to fly into the USA available at well under 24 hours notice, since all this would have to be organised at least 12 hours earlier to get the plane into position and the passengers notified.
And moving passengers to other scheduled carriers within 24 hours? Is this even physically possible given the high load factors most carriers have? What about airports that have only a handful of flights a day in total? And even if getting someone out of Mexico to somewhere in the USA is possible on other carriers, getting them to their actual final destination could be a lot harder, involve multiple connections, and still cause people to miss days at work etc.
Nice idea, I understand where you're coming from, needs a lot more work. There's a reason why the European regulations require airlines to look after passengers during severe weather events (which the US does not do) but set no time limits on how long the passengers have to wait for rerouting. The mounting accommodation costs incentivise the airlines to reroute as quickly as they can, but finding a definition of the maximum time they have to do this in was not possible because of the wide variety of different situations. Ryanair got away for several years with doing a Sun Country and telling people "here's your money back, you're on your own" before the regulators caught up with them, and now they do have to offer genuine reroutes.