I'm guessing it's differences in copyright regimes. At the very least, negotiating streaming rights with major rights-holders in one country must be exhausing and traumatizing. Having done that for one major country (your own home country and primary market), I could understand being hesitant about doing the whole damn thing over and over again in one tiny* country after another, in the face of borderline-chauvinistic media-corporation protectionism (not to mention "cultural protectionism"... I'm looking at you, France).
*Yeah, tiny. USA is a big market. The individual nations of Europe are proportionately little, with correspondingly less return on investment, even leaving aside internal incumbent competition.