Even having ~days would be pretty impractical if it turns out they target a major metropolis. Let's say they target NYC, which had on the order of 18 million inhabitants in 2022. Moving 18 million people in a few days is going to be a major undertaking that few governments would be able to manage without significant prep time. Just imagine the traffic jams you get, exacerbated by cars stopping in the middle of the highway without fuel because the current fuel infrastructure is not going to manage the demand of several million cars passing by. Apart from the amount of people killed, the property damage would be insane.