This is disingenuous. Social security has multiple components, but the main one people think of is called "OASDI", and is a government-run retirement program, not a social safety net. It's paid for by individuals over their working careers through a separate tax (called FICA), and then when retired, they draw out of it, based on what they contributed. Someone who contributes nothing to SS gets nothing out of it, while someone with a high income gets a relatively large pension check. It's not helping the poor much at all. It's just a guaranteed but generally poor-return investment that's mandatory for all working adults.

There are some other components administered by the same agency, including TANF, SCHIP, and Medicare, so yes there is some safety net there, but relative to other western countries it's rather poor. If it weren't, we wouldn't have so many homeless people. America is NOT like western European nations.