Learn German: Nachts steuert uns das Unterbewusstsein. - At night, the subconscious controls us.

This showcases a major rule of German word order. Because the subject das Unterbewusstsein is a full noun, the object pronoun uns jumps ahead of it to sit right next to the conjugated verb. Pronouns are 'lighter' than nouns and naturally gravitate to this spot when the subject isn't at the very beginning of the sentence.

What would the word order be if we replaced das Unterbewusstsein with the pronoun es (it)?

If the subject is also a pronoun, it reclaims its spot right after the verb. You would say Nachts steuert es uns. When you have multiple pronouns in the middle of a sentence, the subject pronoun always comes before the object pronoun.

Is it grammatically wrong to say Nachts steuert das Unterbewusstsein uns?

It is not strictly wrong, but it sounds unnatural unless you are putting heavy, contrastive emphasis on uns. Because pronouns strongly prefer to stick close to the verb, placing uns after a long noun makes it sound like you mean: 'The subconscious controls US (as opposed to someone else).'

Why use steuert for 'controls' instead of kontrolliert?