When can driverless semi trucks deliver goods over the world?

That will not be happening for quite a while. Self-driving involves a lot more than just a fancier cruise control and lane-keeping. Even hacks like Elon Musk had to learn that lesson.

Trains.
Boats.
Planes.

They need much less personnel.
While transporting much more stuff.

When the concept is perfected. Too many things still go wrong to let it happen just yet.

It’s going to be a while for sure. One possibility that may arrive sooner would be a lead truck driven by a human and several autonomous trucks following behind in a caravan. This is probably achievable (with restrictions) using currently available technology. I could for example imagine a group of human drivers driving shipments from the port to a truck stop off of the highway, and then having only one driver lead the caravan across the country on interstates, to be met by another team of drivers navigating the trucks locally at the destination.

I use Tesla’s enhanced autopilot regularly on the freeway, and it is excellent. The hard problems for autonomy are mostly involving city driving with pedestrians, construction, delivery vehicles, police directing traffic, and the bazillion other weird edge-cases that humans can easily reason about, but computers don’t really understand. To get to that point will be at least a decade out IMO. We don’t need perfection for autonomy, we just need it to be several orders of magnitude better than human drivers (and there’s a lot of terrible drivers out there). For interstate driving, we may already be there.

When they build that highway between the US and Europe,

https://www.cnn.com/travel/article/trans-siberian-road/index.html