My thought process is very different from the Orange Man, thank you very much. While I obviously would have to ask experts in this hypothetical scenario about what resources former territories and Cuba would need, my focus is three things:
1: Allow these lands to become prosperous for their people's benefit. This is regardless of whether they become part of the Union as States, or as independent countries. People should live a decent life. Either way, mutual trade is a keystone.
2: Try out different structures of authority for resources and services in each different socialist State. Boring but important stuff, like how many departments are needed to distribute resources, checks and balances, anti-corruption measures, ect. Assuming a presidency of two terms, it is only 8 precious years to figure out a good way forward. Thus, A/B/C testing.
3: If a good model of practical social democracy is developed, try to spread it, and standardize the socialism for the testing States.