A Spanish attempt to colonize Algeria in the 19th century would be interesting. By around 1830 is when it is becoming apparent that the American mainland is lost forever. Algeria might seem like a place to "compensate" if France is not there already.
Plus, the Italians probably have more vivid memories of the Barbary pirates during their lifetimes than the French or Spanish did. I would have to think that the Corsairs treated the ships and villages of the Italian states as easier prey than French and Spanish possessions.
What would British Algeria be like, and what would its impact be?
I would not rule out an Austrian Algeria, in some periods at least. Could've happened before Austria started losing wars in the 1850s.
I think a Austrian Algeria would have been very interesting. It would especially be interesting how the Entente dealt with it, if the rest of history followed OTL pattern.