Using US GDP isn't going to be meaningful since these AI companies probably get at least 50% of their revenue from outside of the US.

Meanwhile, those US mega projects were strictly for domestic use.

It's the same as the Buffet Indicator which for the last 20 years, have flagged the US stock market as overvalued. But when the Buffet Indicator was relevant, most US companies had the majority of their revenue from inside the US. Today, a company like Google will make half of their revenue from outside.