As a non-US citizen traveling to the US, I am obliged to provide the airline and the border control officer with the address of the hotel where I will be spending my first night in the US. (The airline wants it in their APIS documents, the border control officer wants it on the customs declaration.)
I interpret this to mean that I am obliged to have a hotel reservation for the first night.
Now, what should I do if I miss a connection to my flight to the US or if that flight is cancelled? I will then arrive a day later, and in that case I may not have a hotel reservation, and thus I cannot provide a first address.