In the early US, there was a strong assumption that the US would get Cuba eventually by various American politicans. In the 1830s Spain was pretty much broke, so I don't think it'd necessarily be that outlandish for the US to have bought Cuba and Puerto Rico in the period.
The US had a population of around 17 million in 1840. Cuba and Puerto Rico together had a population of 1 million in 1840 and 288,000 in 1837 respectively. The US would suddenly be 7% Hispanic had a purchase gone through.
Had the US purchased Cuba and Puerto Rico in the 1830s, what would be the cultural impact upon the United States?