If you are waiting for MODEL S or Model X
Although Model S and Model X are made in the same US factory as the Model 3 their delivery journey to you is markedly different.
Both Model S and X are shipped partly assembled in containers (3 to a container).
They are moved by road from Fremont to the Oakland Joint Intermodal Terminal where they are loaded on to a train.
The train then takes about 9 or more bone-rattling days to travel to Houston. (actually BNSF Pearland).
The containers are then moved by road to the dock at Barbers Cut
(webcams) where they are then loaded on to a scheduled container ship that eventually arrives 15 days later in Rotterdam (Note: Although the ships have a scheduled stop in Antwerp your containers are unloaded in Rotterdam).
The current shipping schedules show:
Dep Houston Arr Rotterdam
MAERSK IDAHO 24/1 - 8/2
MAERSK OHIO 31/1 - 15/2
SAFMARINE MAFADI 7/2 - 22/2
MAERSK MONTANA 14/2 - 1/3
From Rotterdam the containers are moved by road (or barge) to Tilburg in Holland. Your car is removed from the container and then joins a mini production line where it is reassembled. It is then moved to Zeebrugge and shipped to Southampton.
As can be seen, all this takes time.
Finding your car in this complex logistics chain is difficult but there is a man who can.
@Vedaprime is the specialist in this area. You can find him here but he normally resides on Twitter.