It’s slightly more nuanced. In the case the FBI compelled Microsoft’s US operations, with employees based in the US to access data stored on a server in Ireland and to hand them over.
GP is wondering if no US employees had access to the data directly if US law would have Microsoft US order Microsoft Ireland (which is a wholly owned subsidiary) to transfer the data to the US.
It’s an interesting question. My non-lawyer take, even if they can force Microsoft US to make the request ultimately Microsoft Ireland is an Irish company operating under Irish law. If the data transfer to Microsoft US is illegal, they mustn’t do it.
A situation where this already happens is technology transfers. If information is export controlled (mostly military related), a foreign non-EU/non-NATO owner of a German company can ask and demand as much as they want, non of their employees will ever see that information.