What’s a good app or website that works in most countries of the world and let’s me invest in American stocks?

Due to my job, I have to travel a lot from country to country. Right now, I'm in Bangladesh but will soon move to Germany a few months later. Who knows where to next from there. So I need an app or website that works everywhere and kind of works like a middle man to help me invest in American stocks even though I'm not an American citizen. I tried to install Robinhood but it says it's not available in my current country, Bangladesh.