I bet if I went to India and complained about how pathetic the local hamburger places were, you might wonder about my maturity/worldliness/naivete/etc. You might also rightfully wonder why I was so intent on looking for hamburgers (or Chinese-American food, or Texas barbecue, or whatever) in India, when there are so many other food choices to explore. Every place you go in the world is going to be lacking in some things you took for granted at home, replaced by many other things that are new to you. This is a good thing, not something to complain about, and certainly not something to insult another country over.
Ok, but we're not talking about a specific dish, we're talking about ingredients, so to speak. It's surprising because the US has huge coasts that span climates. I was surprised by it too, and I'm from Spain, whose cuisine is unrelated to India's.
I understand, but it's just a function of what sells and what doesn't. Americans in general aren't nearly as into fish as some other countries, therefore the big supermarket chains don't offer as much variety as some other countries. It's just not a staple in most households.
People who do want more variety go to more specialized stores like Ranch 99 (which is just as American as Safeway, not sure why the poster suggested otherwise), which aren't hard to find.
The poster seemed to blame it on capitalism, but if so I don't see the point in defying capitalism by having the government require the big supermarket chains to stock 100 types of fish that are going to go mostly unsold and get thrown away. That sort of wastefulness sounds a lot worse than requiring the poster to spend 5 minutes Googling for more specialized stores nearby that sells what he wants.