Probably no English Civil War between Empress Mathilda and Stephen of Blois. William Adelin ascends the English throne as William III, thus altering the bloodlines of English Kings.
Mathilda also probably doesn't marry Geoffrey of Anjou. William Adelin was already married to Matilda of Anjou, Geoffrey's sister: unless Henry I wants a double-marriage with Anjou, we won't have any Plantagenêts ITTL. Question is: who might Mathilda marry after HRE Henry V in such a scenario?