Brazilian capital, French river, US city (5)

I believe the answer is:

boise

I'm a little stuck... Click here to teach me more about this clue!

'us city' is the definition.
'Boise' can be an answer for 'city' (Boise is an example). I'm unsure of the 'us' bit.

'brazilian capital french river' is the wordplay.
'capital' indicates taking the first letters.
'french river' becomes 'oise' (I've seen this in another clue).
The first letter of 'brazilian' is 'b'.
'b'+'oise'='BOISE'

Can you help me to learn more?

(Another definition for boise that I've seen is " The capital of Idaho".)

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