Cuba and Vietnam? Really?
Okay, let's start with Cuba. I'm aware of Baptista and Castro and all that, but the US hasn't blockaded Cuba since 1962, the EU is Cuba's largest trading partner, and Cuba survived through the Cold War via subsidies via the USSR. You've also conveniently left out Cuba's human rights record. You could make the argument that normalizing relations would help, but relations with China have been normalized for decades, it didn't make China more liberal. Cuba beats the US in a number of areas (e.g. life expectancy per capita), but Cuba isn't some worker's paradise. There's a reason why even now, people are leaving the island.
As for Vietnam, again, that's a simplification. I'm going to give you the credit of assuming that you know of the history of Vietnam in the 20th century (French colony, then divided between North and South, Vietnam War occurs, North wins, massive Vietnamese diaspora as a result), but I don't see how anyone can claim the moral high ground in that conflict. The North was supported by China and the USSR, the South by the USA and its allies. However, Vietnam is doing much better than Cuba. Paradoxically, it's seen as a key US ally. And a lot of the increases in wealth came from liberalizing the economy, even if the state still has a lot of control.
Frankly, the US is insanely capitalist to me, but those above examples you gave aren't exactly cheerleaders for communism or socialism.