Existence at a place or point of time... i.e. how you are (or how something is). This could also be rephrased as: "However, only ‘used to’ is possible when we talk about things in the past." Some more common examples of "state": "There are four states of matter: solid, liquid, gas and plasma." "He's in a confused state of mind." "Your apartment is so messy! What a terrible state it's in!"

'past states' refers to verbs, not geographical political locations like New York or California. It is used to refer to activities that you did habitually or frequently in the past but don't do now. Ex: "I used to run every day before I broke my leg. " " I used to go to that cafe all the time."