How is galvanic isolation established in an SMPS?
Sure they have transformers: -





The transformer looks different to a regular AC type but it's still the largest single component on the PCB but a whole lot smaller than it would be for 50/60 Hz operation. The transformer is the big yellow taped thing in front of the heat sink at the back/left.

SMPSs also use opto-isolators for feeding back a measure of the output voltage so that it can be regulated. This is another significant isolation feature thus, output and input remain galvanically isolated to several kV and are therefore "safe".