Depends exactly how - but it way well mean Charles Martel gets less kudos, which impacts the Carolingians.
Strong Christian West - it could well lead to Visigothic invasions of Africa in retaliation. Potentially the failure could impact Muslim control in Africa, with Visigothic and Christian Berber alliances throwing rule into chaos and having a Christian Berber state establish itself.
I'd love to see a PoD that involves
John, Count of Ceuta - effectively a different history that leads to a good relationship with the Visigoths, who could assist with a defence of the city, and counter the Muslims in Africa. Could see a Christian Spain, and Christian Berber Morocco.