That is just logically false. It's not even a question of measurement, it is false by definition. The income paid to produce is by definition always sufficient to purchase the output that has been produced. But remember that income paid to the factors of production includes both labor and capital income, because both the owners of capital and the suppliers of labor purchase the products that are created by the combining of labor and capital to produce output.
What is unsustainable is running persistent trade deficits overseas. E.g. by allowing foreign capital inflows, we have allowed the foreign sector to distort prices in an unsustainable manner.
Take what I said with some restrictions, like "US workers can't afford skilled or semiskilled US labor" which is afaict true. I work in production automation, life sciences, and software; my hobby projects in these area are unfortunately quite expensive due to US labor costs. As much as possible I must avoid using US labor if I want to get anything done.
Getting parts CNCed in China may be 10x less than the cost in the US, and materials are a tenth the cost as well (in small qty) as they haven't been transported yet. You can get roughly the same throughput in the US if you want to pay for it, but it will be vastly more expensive.