There are two factors at play here which have to meet in the middle: where is the most efficient place to produce the product and what is the most efficient way to ship the product? The answer to the first question is: wherever has local access to the resources (people, iron ore, etc) and energy required and has the scale required to efficiently build those products. The more cars your country produces, the bigger your factories are going to be, and the more efficiently you can make cars. The answer to the second is by sea. Always by sea. Boats are vastly more efficient than rail, truck, anything.

from: https://www.reddit.com/r/explainlikeimfive/comments/jzhebc/eli5_why_are_ships_more_efficient_at_transporting/

Container ships are reallyyyy big and reallyyy slow so they experience relatively low drag

Drag on a plane is high, they have two massive jet engines that try to push them through the air burning literal tons of fuel to do so. Obviously not the best if you want to be efficient.

Drag on a train scales with the weight of the train. A long heavy train will have more rolling resistance that sucks away energy from it. You can't scale this down without going through and making your wheels harder so they deform less, but you already have steel wheels on steel rails so you're not going to get much better.

Drag on a ship scales with the surface area of the ship that is touching the water, putting more weight on a ship causes a bit more of the surface to touch the water, but not very much. Moving an empty ship is going to use a surprisingly large amount of fuel because the drag is pretty similar, but your fuel consumption isn't going to go up linearly with load like it would for a train.

Consider something like a Maersk Triple E, it carries over 18,000 20 foot containers. It can get them up to 23 knots (26 mph) but generally runs at 16 knots for efficiency and does this with just 80,000 HP of engine capacity. Those 18,000 containers would turn into a train 68 miles long! With 140,000 tons available for cargo, that's just 0.57 HP/ton at full speed, and significantly less at the lower cruising speed(where the ship is built to be efficient). Trains will generally run around 1 HP/ton so this big ass cargo ship is using half to a third as much power to move its cargo.

The downside of this is that it takes 6-8 weeks for a ship to go from China to California, but the upside is that it did that with a crew of just 13 and just had a big diesel running in its happy spot the whole time.