I am a US citizen and my legal residence is in France. Can I open an account with a US online brokerage firm such as e-trade, etc.?
It depends on the broker, IB and Schwab still accept expats. Seems that many other US brokers used to accept expats but tighter tax evasion regulations in 2013 increased the administrative burden on US brokers for US citizens living abroad, most brokers apparently didn't want to bother with this and stopped offering accounts to expats.