A lot of work is moving abroad without becoming imports. US companies own significant chunks of the services and R&D workforce the world over. Even in production, it's not uncommon for a US company to buy a factory rather than importing goods produced in that factory.

That is exactly "export of capital". We also see "import of labor force" since the developed countries struggling with demographic winter.

I didn't mean the point is the imports. The fact is that US is loosing his share of world GDP for decades, and new powers like China are rising. It is just like the decline of British empire at the late 19th and early 20th century and rise of new powers like US, Germany, Japan. We are witnessing the same phenomenon that Lenin called unequal development of capitalism in the imperialist stage. We would also see the same tensions and wars that we saw in the first half of 20th century.

Global GDP is irrelevant for US workers, the value of US exports has grown even as wages stagnated. At some point it just stops being about how much value is produced and becomes a question of how much value is captured.

If a factory produces 10x as many goods with the same number of workers the work those people are doing has increased in value. But, their unlikely to see a 10x wage increase.