> the size of the US economy relative to the global economy is shrinking

This is not true, not at all, it dipped as China grew initially, but looking at the past few years this trend had reversed and the US was again growing as a percentage of the global economy, going from a low of about 21% in 2011 to nearly 27% today. It seems certain now that Trump has put a bullet in this growth, but it was hardly inevitable. In 2024 the US was in an incredibly strong position relative to the rest of the world.