That’s a very good question and an important one. The answer is Yes. You can as a retail investor from India invest in US stocks and ETFs. The instrument that can help to do exactly that is Vested(www.vested.co.in). They are registered with the US Securities Exchange. Currently, they have an offer where they are allowing new investors to open an account totally free of cost.
The best part about Vested is that they allow you to buy fractional shares of any listed US company. That means if an Amazon stock let’s say costs $1000 and you have $100 then you can purchase 0.1 shares of the company. They also have curated mutual fund themes through which they allow you to invest in other global markets like China, Japan, etc.