Why stay at a hotel and book a ticket for a few days later?
The reason is quite simple: Yang Yi isn't actually afraid of the ordinary police finding him.
Though the United States seems calm on the surface, there's a storm brewing underneath. Secret organizations like the Grey-cloaked People and Cleaners don't have many people; even if they want to find Yang Yi, they'd largely rely on the U.S. authorities.
The death of a CIA deputy director with real power would be an extremely sensational event for the entire intelligence system of the United States. Whether it's the CIA or the Department of Homeland Security, they must now be working at full capacity to ferret out Yang Yi, who, even if not the perpetrator, certainly has a significant connection.