Edit to elaborate, GDP is calculated based on final goods and services, outsourced work exclusively counts towards the GDP of the country that work is done in, and only affects the GDP of another country when they buy what the first country made, but the outsourced work still happens in country A, so country A gets all the GDP created by selling finished goods, and all the GDP of the work done on unfinished products within their borders.
Basically, the US isn't sitting on everyone else's money, it just genuinely makes and sells that much shit