If they take over Iberia, they will move into Septimania and Provence. Being more advanced (and richer!) than Europe, more Viking efforts would be directed their way. Eventually France (maybe not under the Karlings?) would unify, and eventually they would die under the combined weight of France/European effort and internal pressure.
In OTL the Reconquista was an effort that took place over about six centuries, only ever advancing slowly. As soon as Europe overtook the Muslims in technological advancement (1258 would be a good point to base this off), the Arabs would be pushed back. Grenada might last longer, and Spain may be stronger, or possibly weaker in the following centuries. Maybe the rush into America would be delayed a century (England and the Dutch only joined to gain the prestige of New Spain).
- BNC