QQQ is not in isolation. It’s just a bundle of stocks. Rebalancing that will affect the prices of its constituent stocks, which include some of the highest market cap stocks. Those same stocks are also in many of those other popular market-cap weighted indexes (VTI, VOO, SPY, etc). Price action originating from Nasdaq 100 rebalancing would affect everywhere else those stocks are held. Which is a lot of places.

Except those other indexes won’t have SpaceX. Suggesting any index price moves would be … asymmetric at best.

Now it’s being reported that they’re angling to get SpaceX in the S&P 500 index as well [1]. Maybe if all the indexes get it then it balances out everywhere, who knows. This whole event would be in beyond unprecedented territory.

[1] https://finance.yahoo.com/news/p-weighs-rule-changes-speed-1...