This is a misunderstanding. The Federal government has a small set of powers because almost all legal and political power is vested in the individual States, which have most of the remit and authority of sovereign countries. Americans have always lived under the expansive social policy regimes of their respective States, which vary widely. It is only in the 20th century that the Federal government started dabbling in social policy at all.

Every State I have ever lived in had their own unique minimum wage laws. The Federal government is more like the EU, much of its policy function is to harmonize the laws of the States. Americans have almost no interaction with the Federal government; the laws they live under, the taxes they pay, and the social programs available to them are almost always specific to the State.