Not sure what you mean by "US people" - the PC is mostly (but definitely not 90%) US based, but that follows from systems research being largely US based (for now, at least).
90% of systems researchers are not US-based. My point is that it didn't embrace global leadership in systems research as a conference. It died because it didn't grow. Eurosys was created as a counter-weight to Europeans not being able to get on the PC of conferences like Usenix ATC. It's still going strong.