Nearly all Dutch speed skaters are from a single province (Friesland) in the Netherlands with just 600k inhabitants. That's where the facilities are and where it is a popular amateur sport. With global warming, countries where speed skating was more of a thing to do outside during winter, but who don't have that many advanced facilities like the Dutch, lost a lot of ground (Scandinavia, Russia, Germany). Speed skating that exists in other countries is often more focused on short track skating, which is not that popular in The Netherlands.
The American Shani Davis had very good results. But the reason why he started skating is because he has parents who were very much into speed skating and who pushed him into it, not because his peers pushed him into it, like what you would see in Friesland. Another American, Chad Hendrick, switched from inline skating to ice skating. He was competitive very quickly, but I bet that a lot of people will have a lot of trouble learning the different techniques.
So the pipeline to professional ice skating is very lean in the US, where a lot of stars have to align, where it is very wide (and competitive) in The Netherlands. If a skater can beat the Dutch competition, (s)he can often beat the international competition.
There is actually a worry that long track speed skating will be reduced in scope at the winter Olympics and the Dutch speed skating union has given help to foreign competitors.
It's easy to look like you have a doping advantage when others simply do poorly. I'm not saying that Dutch ice skaters don't dope, but I don't think a special advanced doping program explains their success.