Sunni Islam has no clergy, no ordination, no synod and no pope, and it is worth being precise about what it has instead, because the absence of a hierarchy is often mistaken for an absence of structure.
Authority rests with the ulama, the scholars, and their standing derives from training and recognition rather than appointment. What they work with is a developed legal science, fiqh, drawing on the Quran, the Sunna, analogical reasoning and the consensus of qualified scholars. Sunni Islam recognises four schools of law, Hanafi, Maliki, Shafii and Hanbali, as equally valid. A Muslim may follow any of them; they differ on details of ritual, contract and family law and not on fundamentals; and this arrangement gives the tradition legal breadth without a central authority able to impose a single answer.
Geography settled the distribution: Hanafi across Turkey, Central and South Asia; Maliki across North and West Africa; Shafii in Egypt, East Africa and Southeast Asia; Hanbali chiefly in the Arabian peninsula.
Theology divided too, less visibly. The Ashari and Maturidi schools, which affirm God's revealed attributes without asking how they are held, became the mainstream against both the rationalist Mutazila and a strict literalism. The Athari or traditionalist current, associated with the Hanbali school and with Ibn Taymiyya, rejected speculative theology altogether, and it is the ancestor of much modern reformist thought.
The point that follows from all this is practical. There is no Sunni body that can excommunicate, define or bind. Fatwas are opinions, and their force depends on the standing of whoever issues them, which is why a single question can draw contradictory rulings from different scholars with no mechanism to resolve them.