Which ones?

If you’re thinking Scandinavian countries they are mixed economies. Most successful economies today are mixed economies.

All economies are mixed, save for North Korea, which is command economy communism.

On the sliding scale of welfare state socialism, Finland and Norway have the greatest degree of public investment. Angola would be on the other side of that spectrum, with almost no public services or redistributive programs offered.

When people want to introduce Scandinavian-like social programs to the US, it's "socialism doesn't work". When people point out that they work in the Scandinavian countries it's "Those aren't actually socialism".

When people want to claim that socialism works, they point at countries that aren't socialist.

Socialism is very well defined and it's made nebulous only to claim virtues it doesn't have.

Scandinavian countries aren't socialist. They themselves say they are not socialist and a simple google search for "are scandinavian countries socialist?" will show you that the consensus is that they are not.

Good news. The US can implement universal public healthcare and free university without fear of being socialist.