I was recently looking for US stockbrokers who are able to open accounts for foreigners (non-resident aliens) from most countries. Surprisingly few brokers are willing to open an account for non-US residents, and some of those who do accept international clients only accept those who live in a small list of countries. Perhaps the paperwork and administrative burden for accepting international clients is too high for most brokers. Here I will be focussing on those US stockbrokers who offer their services to a nearly global client base. In other words, those who can open accounts for residents of most countries of the world.
TD Ameritrade is a large brokerage firm, and opening an account is straightforward for international clients. All you need to do is sign up online, and fax the required documents according to the instructions. There is no minimum account balance required, and commissions for most transactions are zero. Options, futures, and currency trading may require minimum balances and/or approval. Their customer support is known to be good. They provide lots of trading tools to the regular user, including news feeds, a trading platform (Thinkorswim), fundamental data, and an API.
Firstrade is a smaller brokerage firm. Zero commissions for most trades. Compared to TD Ameritrade, it has less tools, but this should not matter if you are just looking for a broker to simply buy and sell. It provides fundamental data from Morningstar.
Interactive Brokers is a large brokerage firm. Unlike the other US stockbrokers mentioned, Interactive Brokers allows you to access a global market, not just the US market. However, there is a monthly account maintenance fee if you have a small balance. Interactive Brokers provides lots of research data (including fundamental data from Refinitiv) and an API. You may want to weigh the monthly maintenance fee against the convenience of access to global markets when choosing Interactive Brokers. It charges a low (but non-zero) commission for trades.
Charles Schwab also opens accounts for non-residents, but they have a minimum balance requirement. I have not tried to open an account at this one.