Well, to be fair, AMS-IX is located around the Amsterdam Area (a circle of around 30 km orso), while DE-CIX has locations in the US as well.
I'm not familiar with the specifics, but based on these locations, I'd say AMS-IX is the biggest internet exchange serving europe.
Both DE-CIX and AMS-IX have exchanges in NYC now. Both have actually started branching out and building exchanges in many new cities. The traffic levels they're talking about are specific to both of their home markets (Amsterdam/Frankfurt).
The DE-CIX graph seems to be about the Frankfurt exchange. AMS-IX doesn't just serve the Amsterdam area, it's where many undersea cables from North America and the UK enter the European mainland.
I'm more surprised that 'List of Internet exchange points' isn't dominated by North American and Asian exchanges. Do they have a larger number of smaller ones?
My traffic in philippines would actually go out of the country and back in, occasionally via los angeles (like 500ms+) because the incumbent monopoly telco refuses to peer with any other isp, so if you don't use them your traffic is intentionally screwed [there is an IX there for small ISPs, the 99% market share one just doesn't peer there]
Aside from singapore, every other country has something approaching this level of fucked-ness - HK to CN traffic often goes via LA/seattle, TW to CN traffic often goes via LA/seattle, all of china telecom's peering links are oversubscribed to death anyway and fall over during peak hours, a lot of the SEA traffic i've seen traverses singapore or worse, even if it's entirely domestic bound
no, Amsterdam does not have the size amount of peering it does because of submarine cable landings, and DE-CIX is largest by bits exchanged in one single metro area (Frankfurt)