Fun facts about US electricity distribution: you might share your 120V/240V service with many other homes! It is not uncommon for a single transformer to service multiple homes. This means that the voltages of your two 120V feeds may be impacted not just by your loads, but by those of your neighbors. And of course the transformer and its upstream power source.
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And the other side of that transformer? It could be anywhere from 480V to 34,500V! That's a spicy zap!
Fun fact: 34.5kV is considered "medium voltage".
If you're in a bigger multi-unit building like a condo or apartment complex you might not have 120/240 at all! You might have 115V/208V service instead. This is a common step-down from 480V three phase.