better question, why does only the UK use that naming practice?

The adjective-noun or noun-adjective word order is one of the attributes of every language. Joseph Greenberg touched on this topic in his groundbreaking work Universals of Language. His work noted correlations between linguistic features in languages, and some of these include correlations between adjective-noun word order and syntax, which is the order that subjects, objects, and verbs come in a sentence. He noted (§5) that all languages with SOV syntaxes and the genetive after the noun also have the adjective after the noun, and (§17-s) that most VSO languages have the adjective after the noun. So some languages put the adjectives after the noun because their syntaxes are built that way.

He also noted (§19) that languages in languages that normally have descriptive adjectives before the noun, there are no exceptions when descriptive adjectives can come after the noun. This is the case with English. BUT naming adjectives, like the examples you mentioned, can come after the noun. This is because names often function different linguistically from other adjectives.

And it isn't just a North America thing. In Spanish and French, which are spoken in North America, the word "rio" or "Rivière" comes first.

TL;DR: Some language syntaxes preclude having adjectives before the noun. But it's not just a North America vs the rest of the world thing.

Greenberg, Joseph H. Universals of Language. 1966.

You might get more of the answer you're looking for over at /r/linguistics

Hello everyone,

In this thread, there have been a large number of incorrect, speculative, or otherwise disallowed comments, including many asking about the deleted comments, which merely compounds the issue. As such, they were removed by the mod-team.

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I have no idea precisely why this is, but I can tell you that it's partially a regional and temporal variation within the United States.

The word "river" is frequently applied in other Englishes to a size of stream that would by modern Americans to be too small to be considered a "proper" river. Generations of Americans have traveled abroad and been disappointed that fabled watercourses like the Avon and the Jordan would be considered unremarkable creeks back home.

Partially this may be because there's only a handful of rivers on Earth that rival the Mississippi and the Ohio in size and discharge, but I think it's also because many of the smaller watercourses in the United States have other names, often derived by different colonial pasts.

This semi-famous map shows the usage of generic terms for higher-level watercourses in the continental United States. Notice that "brook" is largely restricted to New England and New York State (as well as Northern New Jersey, tellingly). In contrast, "run" is largely restricted to northern Appalachia and parts of Ohio. "Swamp" is mostly used for slow-moving rivers on in the coastal plains of the Carolinas.