Apple has one (1) datacenter in the entire world, and it's in the USA. How good do you think the latency from Holland will be? Google has datacenters in Groningen and Eemshaven, and all over Europe.
You are wrong about Apple, they have one huge datacenter in the US where people suspect the Siri backend runs. They also have a smaller data center in California. We don't actually know what runs where, and we don't know what they are running in leased space in 3rd party datacenters. And, they are building other datacenters in the US.
In any case, wherever Siri runs, I don't think that Internet latency comes close to explaining the latency, and, I think, Siri can actually hide a lot of latency.
In any case, wherever Siri runs, I don't think that Internet latency comes close to explaining the latency, and, I think, Siri can actually hide a lot of latency.