So in OTL California became part of the US in 1848 after beforehand claiming independence from Mexico because of, from what I understand, a steady influx of US migrants. So a few possibilities spring to mind. 1) Could California have remained independent, being squeezed between Mexico, US and (barring Oregon) Canada? 2) Could California have remained part of Mexico, or was the demographic change leading to an inevitable secession? How would a Mexican California have evolved? 3) Following on 2, was the demographic change in itself inevitable? Could have Mexico/Spain have had a settling and migration policy of their own? How would Mexican and American settlers mix if there remained a Mexican majority, or a 50/50 ratio ?