Is the Dalai Lama the Head of Buddhism?

No. The Dalai Lama is the head of the Tibetan Government in Exile. He is not even the head of any of the 4 schools of Tibetan Buddhism (Sakya, Gelug, Nyingma, and Kagyu). In fact, the 14th Dalai Lama's political role in Buddhism has cause many problems within Buddhism. He has caused huge divisions in both the Kagyu and Gelug traditions. Search 'Dorje Shugden Controversy' and 'Karmapa Controversy' on google or click on the related links below to learn more about problems in Tibetan Buddhism created by the 14th Dalai Lama.