I know that among Dutch writers, it is a public secret that one does not have an English translation because the US (and rest of Anglosphere) is an interesting market, but it's a requirement for getting on the NYT bestseller list. This means worldwide visibilty and worldwide sales. I never managed to get hard numbers from anyone, but reading between the lines, Dutch and American book markets appear to be on the same order of magnitude, not necessarily in favour of the US.