Why is it 'meaningless'? It gives you some idea of the scale of (US) data centre energy use in comparison to all other energy use. It might be useful to know if the US-data-centres:US-energy-use and worldwide-data-centre:worldwide-energy-use were particularly different figures, but it's still a useful number. And it shows why it's a good idea to put datacentres in places where the electricity supply is relatively low-carbon. Not as important as putting aluminium smelters there, but still worth doing if you can.