If you care enough about 911 and emergency situations to be reading this article, and you don't have a landline, then that's on you for being irresponsible. People spend more on texting than it costs to have a landline.
Every line in the US is required by law to be able to dial 911, even if you aren't paying for any service at all. This applies to landlines and cellphones. I often keep the police scanner on as background noise, and I can say at least a quarter of the 911 calls in Memphis originate from disconnected cell phones. If your landline gets a dial tone or your cellphone is charged and has a signal, you can dial 911 whether you have a phone plan or not.
Of course that doesn't help in the event of a 911 outage but those are, fortunately, quite rare. I can't justify $50 a month to pay for landline service in the extremely unlikely event that both the cell network and the local 911 network go down. If something like that occurs, there's been a catastrophic event on a scale where emergency officials aren't going to be much help anyway.