Which phrase does NOT contribute to understanding language distribution on maps?

The phrase that does not contribute to understanding language distribution on maps is the differences between American and British English. This distinction primarily relates to variations in vocabulary, pronunciation, and grammar between the two forms of English, rather than illustrating how languages are distributed geographically.

In contrast, historical trade routes are essential to understanding language distribution because they highlight pathways through which languages can spread and influence each other. Colonial expansion played a significant role in the spread of languages, as colonizers often imposed their languages on indigenous populations, leading to wide-reaching linguistic impact. Additionally, population migration patterns are crucial in mapping language distribution since they show how and where different language speakers move, leading to changes in linguistic landscapes and the emergence of new dialects and languages over time.