You have to be more specific when talking about "socialist europe". The Netherlands, for example, has the best-managed pension system in the world. Despite what many people believe, "Europe" isn't one country and it doesn't have a single healthcare system, pension system, or anything else related to the welfare state.

US social security on the other hand is exactly as you describe pension systems in "socialist europe". Money taken from current workers and invested in state debt.

https://www.mercer.com/en-au/about/newsroom/mercer-cfa-insti...