Awkward yes, ashamed no. And this is a common occurrence for Chinese people. I just chalk it up to the fact that China is a culturally, and linguistically, mostly homogeneous society. They probably aren't even conscious of the fact that other Asians are common in the west. Add to the fact that most Chinese immigrants or expats only hangout with other chinese people anyways. But to your point yes, they should ask first.

Rude to come to others with any stereotypes based on their look. Assuming someone is Chinese and interacting with them in a certain way bearing that thought itself is disrespectful of others identity. They may be unaware of what that means, but you shouldn’t in any way feel ashamed

Just said you are American (or Canadian...etc. wherever you grew up). Not all Asians speak Chinese.

A lot of people have come up to me and speak English. And I look Asian.

I’m Japanese living in the UK, and my area has a large population of Hong Kongers. They come up and talk to me in Cantonese. Some Brits come say hi in Mandarin. Some people ask me where I’m from, it gets me confused because my answer depends on whether they’re asking this due to my ethnic appearance or my accent from Pacific Northwest, but I hesitate to give a whole background speech which is not expected. An American once asked me what my story was. I liked how he tried to get to know “me”.

no lol i speak fluent chinese but i pretend im not when they come up to me so i don’t have to listen to them yap about something irrelevant to me. and idfc what they call me, no one is obliged to learn a language to cater to someone’s needs 😩