In the context of media and popular culture, 'monoculture' refers to the phenomenon in which large segments of society share common media consumption and associated cultural references. This phenomenon peaked in the mid-20th century to the early 2000s--examples include artists like The Beatles dominating music, TV shows such as Friends commanding over 50 million live viewers in the US alone, Bollywood films like Dilwale Dulhania Le Jayenge uniting audiences across India and its diaspora, and telenovelas like Yo soy Betty, la fea captivating viewers from Mexico to Argentina.
In contrast, today's media landscape is much more fractured, and strangers typically share little media consumption in common.