The difference being in how those social programs were implemented and the taxes raised to cover the costs of them.
The USSR had a high cost in the military and suffered from economic stagnation. Unable to grow enough wheat they had to buy from the USA to feed their people.
Greece didn't raise taxes enough to cover their debts from social programs. As their economy grew worse the cost of health insurance rose and costed more.
A lot of European nations can afford socialist programs because they don't spend a lot on their military due to the USA protecting the European coasts after WW2.
Canada also does not spend a lot on their military due to a partnership with the USA to protect their coasts as well. So they have more money for socialist programs.
Japan and Britain haven't really been able to feed themselves for a 100 years. The Soviet Union before 1965 had high growth rates.
My thoughts are that when a countries central powers make good bets on human capital, infrastructure, and technology, then market economies can feed off of those and produce high rates of growth.
Brezhnev and his compatriots in the soviet union never let a vibrant consumer economy develop. And growth stagnated. Faced with the same problem in the early 80's the Chinese Communists implemented market reforms. That combined with previous investments in human capital, plus sometimes heavy handed restrictions on population growth appears to have been successful. (Also the Chinese were able to cut a deal with the US and Europe to allow mostly unfettered access to developed world markets, which the Soviets didn't have)
The USSR had a high cost in the military and suffered from economic stagnation. Unable to grow enough wheat they had to buy from the USA to feed their people.
Greece didn't raise taxes enough to cover their debts from social programs. As their economy grew worse the cost of health insurance rose and costed more.
A lot of European nations can afford socialist programs because they don't spend a lot on their military due to the USA protecting the European coasts after WW2.
Canada also does not spend a lot on their military due to a partnership with the USA to protect their coasts as well. So they have more money for socialist programs.