It's a neutral exchange. Note that it doesn't give the whole story; really big players like Netflix may have hardware directly in some of the ISPs and bypass the exchange completely.

The US doesn't have many significant neutral exchanges, but here's one: https://www.seattleix.net/statistics/

Possibly, but Netflix do peer in INEX, https://www.inex.ie/ixp/customer/detail/103

They do, but they likely also have equipment in many of the ISPs.