That effectively restricts Spain (or, more accurately, Castille) to the nothern Atlantic though, unless they can find a workable 'North-West Passage', because without being able to sail aorund the southern ends of either Africa or South America they are blocked off from the Pacific.2) The Treaty of Tordesillas in 1494 was the original agreement which divided the world between Spain and Portugal and set up the original spheres of colonization. If this changes, you could see very different colonization. For example, during this time period latitidue was MUCH easier to measure than longitude so maybe rather than dividing the world East/West it could be divided North/South so that Portugal gets all lands South of the equator while Spain gets all lands to the North. This would still give Portugal what they want (a route around Africa to Asia) and Spain what they want (colonies in the region discovered by Columbus), so I think it could be plausible??
And what they originally wanted, and financed Columbus in the hope of, was a westwards route to the Spice Islands...