You are comparing the total market value of NVIDIA to the sum of all transactions in a country for a year. Saying NVIDIA represents 16% of the GDP would only be true if the sales revenue of NVIDIA is 16% of the GDP, which it's not.

Yes, no. Market cap and GDP is very different thing.

To my understanding, Market cap is the total number of shares multiplied by its current price. To do an experiment, if we were to sell those shares, the price would start shrinking, and so would the market cap, way before we can get that kind of money

The market cap is just a reference value, not a count of sonething really happening in the economy. It represents sonething more like investor expectations.

The comparison to GDP is interesting, but it doesn't represent what it looks like.

GDP is, in itself, a reference value that represents a few things, this time it does stand for something happening in the economy, it kind of estimates the value added by the economy at current prices.

A better way to describe how important invidia is in the US, you could compare all revenues by all companies, and see how much Nvidia represents over that. I don't know if we have that kind of number.

But to give an idea, we would instead look at the number of employees in Nvidia in the US compared to the total number of workers in the US

We are looking at a total of 161 million employed people in the US

https://www.bls.gov/cps/cpsaat18b.htm

And a few sources tell me 30k employees in Nvidia globally! Let's assume they are all in the US.

So you see that what you claimed would mean that this 0.02% of workers in the US account for 16% of the totalUS output. Which would be insane

I hope my reply helps you, I'm also learning, there's no shame in that