Tikka Masala is an Indian-Inspired dish which was invented in the UK by people with Indian cultural heritage. That's about as concise a description as you can get without running into difficulties of definition - there's no consistent way of defining what "being a dish" means without running into contradictions.

In fact General Tso's is the perfect counter-example: Multiple Chinese people have told me they enthusiastically disown General Tso's Chicken and explicitly call it American food. So if we say "a dish belongs to a country if it's invented there", then Tikka Masala is British (which I agree "feels" wrong); but if we say "a dish belongs to a country if it was inspired by the cuisine of that country", then General Tso's is Chinese, which, apparently not!

And that's without even considering the question of how far "back" you should go with inspiration - what if a dish was inspired by how the Indians used food they got from the Persians who traded it with the Chinese - is it Indian food or Chinese food? (Idk if that's historically nonsense, but you get my point) Why is the most-recent ancestor more important than the environment of creation?