The account which you use when setting up your echo is the one whose store you're stuck with.
No idea about the situation in France but here in The Netherlands most people I know use the USA or the UK store, because of missing skills in the Dutch store. I do, because I need the harmony skill. However, this way you miss out on local stuff
(unless someone is nice enough to publish their skill in other stores as well, dome Dutch news organizations have, yay).
Would be nice if amazon figured out the internet is GLOBAL, right