Which term describes something that is occurring in many places or affecting many people?

The term that describes something occurring in many places or affecting many people is "widespread." This word conveys the idea that a phenomenon is not limited to a specific location or group but is instead spread out over a large area or across various groups of people.

"Localized" denotes a situation or condition restricted to a specific area or community, which does not align with the concept of widespread occurrences. "Ubiquitous" implies being present everywhere at the same time, but it carries a slightly different connotation, suggesting a constant and pervasive presence rather than simply being widespread. "Commonplace" refers to something that is normal or typical, and while it may occur frequently, it does not necessarily imply that it is affecting many people or places at the same level as "widespread."

Thus, "widespread" accurately captures the essence of something that is broadly distributed or influential across various locations or populations.