Complex sentence: During the early 1970s, influenced by the U.S. gay liberation movement and the 1968 Tlatelolco massacre, small political and cultural groups were formed; initially, they were strongly linked to the political left and (to a degree) feminist organizations.
Split into simpler sentences: During the early 1970s, influenced by the U.S. gay liberation movement and the 1968 Tlatelolco massacre, small political and cultural groups were formed. Initially, they were strongly linked to the political left and, to a degree, feminist organizations.