Have fun. Logistics are a killer.
Against Cuba, you're up against the Spanish navy and empire, and the US was pretty small and weak in AJ's time.
Moreover, the rebels in Cuba fighting against Spain would just as cheerfully fight against the US - which would want to keep them as slaves.
Against California. Ouch. How do you even GET there?
Do you conquer Texas first, then New Mexico and Arizona before conquering California? 1000 mile supply lines in hostile territory?
Not saying either is technically ASB, but the sheer height of the hurdles to be crossed is overwhelming.
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Cuba: if Spain and Britain were involved in a war over Gibraltar, say, then the US could defeat the Spanish forces in Cuba, I suppose. Can they also HOLD Cuba? That's the next question.
California. ...
Have AJ ally the US with France in a puffed up Pastry War, US forces join with French ones in taking Veracruz. The French insist on totally unreasonable demands (why?) from the Mexican government, which totally unreasonably refuses to negotiate (why?). Both sides refuse British mediation ('cause everybody's drinking lead paint?)
Franco-American forces take Mexico City. France installs a puppet government, which promptly signs all of northern Mexico (i.e. California to Texas) over to the US.
American forces leave 'Mexico' (having 'won'), and start fighting all the locals from the Sabine river to the Pacific.
Without a functional Mexican central government, there's little support for the locals, and after an extended fight (probably a decade) the US finally takes possession of all that land.
Now, why the US would agree to any of this, especially the huge (by US standards) standing army and the massive increase in taxation it would require, is quite beyond me. But someone MIGHT be able to fill in the blanks.
Really, really, really improbable.