Doesn’t this apply to both the US and socialist countries?

Yes, but I think you’re hitting on the wrong point here. The point is that countries themselves cannot change their power overnight, nor their structure. Cuba cannot hope to punch at the US as the US is the global Imperialist Hegemon, and has been so for a century, even if it is steadily improving conditions for its own citizens over time.

I guess I’m also not very clear what people mean when they say socialist country. Capitalist with good regulations? No money? Government owned businesses?

You’re on a Marxist community. Socialism in Marxism refers to the Dictatorship of the Proletariat, ie shifting State Power from Bourgeois control to Proletarian control. An economically fully-Socialist country is going to be focused on central planning and collective ownership and direction of production, though Socialism itself is a transitional status to Communism eventually.