Unless Mexico manages to promote colonization to the northern territories and attract settlers of Europe, I can't see Mexico laying claims on the Oregon territory, there wasn't enough population, even for California, New Mexico and Texas, but it's possible, specially if gold is discovered in California, however, that could attract unwanted attention on the zone from Britain and the US. Mexico could aid the Cuban rebels, but I don't think Cuba would be annexed, Mexico would need to do something about it's navy, which was practically unexistant at that time. As for the Indian territory, how could Mexico could annex it? It was US territory after all.