I couldn't possibly choose between Indian, Italian and Mexican.
Sure there are dishes in all 3 categories that are long and time consuming, but my go to quick and easy meals are red lentil and spinach coconut milk curry over quinoa, whole wheat penne pomodoro in the summer, and with broccoli and cashew alfredo in the winter, burritos made with crockpot pinto beans or tacos with red lentil-nut filling, cabbage avocado and lime. Or white bean and kale soup with garlic, lemon and sage and broiled polenta croutons, which is easier than it sounds and sort of Northern Italian.
My Japanese cuisine is limited to veggie sushi, miso soup and edamame, and I seldom make those.
I can't think of any Russian or Vietnamese recipes that I make regularly.
I suppose you could call my hummus/quinoa tabbouleh-esque salad/melon/pita and crudite supper sort of quasi-Greek or maybe more middle eastern. The only other thing that I ever make that's Greek is spanakopita, and that is DEFINITELY neither quick nor easy.
I don't consider my Chinese dishes quick and easy. Too much chopping, and I like to pre-fry my tofu. Plus brown rice takes a long time to cook. I do a stir fry once a week or more, but it is not on my "need a fast meal day."
Thai's not bad if you use store-bought curry paste. Never tried it scratch cooked. Still. Lotta chopping, and see my above note about cooking time on rice.
Ah, American. Shake and bake tofu strips are pretty quick and easy. Lentil loaves, barbecued seitan ribz and burgers too. But the thing about American food is that it needs side dishes, and those are a pain.