This is a useless “technically correct” rejoinder. Yes, the top 500 would by definition still have 500 companies in it. Yes, the net value of the s&p would almost certainly be lower without the innovation brought by immigrant founders. Which is obviously the point being made.

H1B started in the 90s, when the economy was at all time highs, and since then growth has been less impressive.

It is your comment in fact that decided to assume I missed the point, while assuming something that’s almost certainly not easy to assume.

That is half true. It also would be a USA without Apple, Nvidia, Google, Tesla, Intel, Qualcomm, Yahoo, Paypal, eBay, Pfizer, P&G, Goldman Sachs...

Not really. Companies would still be founded, but there's no way to tell if they would ever grow to the point that would be listed in the S&P 500.

Not sure if you don’t know how they define the S&P, or straw-manning.