The title points to Las Californias in 1769, and the poem seems to speak in the voice of people already living there, though the text itself never says who "we" are. Judging by the setting the title suggests, the speaker looks at newcomers from the outside and sees them as strangers.
The first two lines set up a contrast. "The land has been our home" is calm and plain, a statement of belonging that needs no proof. Then "they have walls" arrives with a jolt. Walls mean separation, ownership, keeping things in and out.
The second stanza turns that idea inward. If the outsiders build walls on the ground, they also carry them in their heads: "in every mind a box / they call God." The speaker seems puzzled, even critical, that something so vast gets shrunk into a container.
The mood is quiet but sharp. There's no shouting, only short lines and a steady, observant tone that makes the contrast feel like a verdict.