Using street lamps as EV chargers

Presumably most US street lamps are 120V which is probably why we see this idea implemented in other countries that have 220V power everywhere.

Also worth noting that many towns in the US don't have street lamps or only have them in the CBD.

I don't know how standalone street lamps are wired in cities, but basically every US residential service transformer has 240v.

Most street lights are either 240V or 480V single-phase, the higher voltage allows for smaller conductors over longer distances. Shorter, more decorative pole lights (say in a CBD) might be 120V.

Commercial pole lights can be 120V but are usually 208V (for 208V 3-phase services) or 277V (for 480V 3-phase services) in practice.

Your presumption is probably incorrect for a large number of lights. From what I've seen most streetlights around me in residential areas run off both mains with the neutral disconnected, implying they're running off the full 240V. Bigger lights probably run off even higher voltage runs.

Its a common misconception the US infrastructure is a 120V system. Your home has 240V and likely even has 240V appliances connected. Your individual outlets are only connected to one half of that 240V service.