green tea and matcha is sold in the states, but can be hard to find sometimes. it's mostly sold as tea bags, but many coffee shops like starbucks sell matcha lattes. green tea isn't very popular though so it's difficult to find a good brand. i tried buying a bottle of ice green tea the other day and there was so much sugar in it that it didn't even taste like green tea. 😅 also i'm suprised nobody mentioned daifuku mochi! ice cream mochi has become fairly popular in america recently. my local grocery store sells ice cream mochi, but i wish they sold anko daifuku too... my aunt specially ordered some to share with us for christmas last year and it was really good. i want to eat it again.
pocky is quite popular so it's already sold in america. america only has strawberry pocky and chocolate pocky though, so another flavor might be a good souvenir