Learn Portuguese (Portugal): Se tu governasses o país, tínhamos liberdade. - If you governed the country, we would have freedom.

This is the Imperfect Subjunctive form of the regular AR verb governar for tu. We use this tense after se (if) to talk about a hypothetical situation. For regular AR verbs, you form the tu conjugation by adding -asses to the stem.

The translation says 'we would have', so why does the Portuguese use tínhamos instead of the conditional teríamos?

While teríamos is grammatically correct for 'we would have', in everyday spoken Portuguese it is very common to replace the Conditional tense with the Imperfect Indicative (like tínhamos). It means the exact same thing in this type of 'if' sentence but sounds much more natural in conversation.

Why is the pronoun tu included, but nós is left out before tínhamos?

In Portuguese, verb endings usually tell you the subject, so pronouns are often dropped. The ending in tínhamos makes it perfectly clear that the subject is nós (we). The tu in the first half could also be dropped, but including it adds a little emphasis: 'If YOU governed...'.

How would the verb change if I wanted to use você instead of tu?