Is the clause in parentheses an adjective or adverb clause Mom wouldn't let me go to the party (until my room was cleaned).?

The clause in parentheses, "until my room was cleaned," is an adverb clause. It modifies the verb "let" by providing a condition under which the action of letting me go to the party would occur. Adverb clauses typically answer questions like when, why, or under what conditions.