This is what I think the difference of NY and Japan.
Every single shop you walk in, do you say "hello" to saler? Yes in NYC or in foreign country. Open the door, "Hi, how are you?" is the common sense for them, to let them know you are a customer and not the suspicious shopper.
Greeting at shop you go include convenience store, department store and every kind of shop is not custom for Japanese, of course you would say hi at legester but not necessary. Less conversation with stranger in Japan.
You hear "Irasshaimase" : "welcome to our shop" at Japanese shop, this not mean "hello, how are you?" that's why no need to respond to this greetings. Just give them smile as a respond.