The chart measures CGT, Container Gross Tonnage. This is a subset of GT, Gross Tonnage which is calculated based on "the moulded volume of all enclosed spaces of the ship". This chart measures the countries of origin of top manufacturers of container ships.

An aircraft carrier, as an example, would have comparatively low CGT.

list of largest GT ships list of largest container ships

Jones Act

The US has a massive trade imbalance. They buy way more than they sell and export freshly printed dollars.

I suspect the proportions of those bars are similar to the actual import flows, meaning those who import goods into the US are the ones doing the shipping.

Why? Because the US knows how badly the world needs dollars, so they can afford to just wait for stuff to be brought to them.

Don't think the numbers matter. It's not always about quantity, it's the quality. And China can't stand the quality that America boasts of. Else, why would China let US Naval ships in the South China Sea for years now.