No, you are not.
That's taking the premise way too far. Slaves were owned as property. You are not property of a corporation just because your job is connected to a visa. You don't have slaves rights (almost entirely non-existent human rights, specifically). You chose to immigrate, there is a system involved in that, you knew that ahead of time, you chose to go forward regardless. You did not become a slave in the process, you did not sign on for 'slaves rights' in the process, you did not abdicate your freedom. Your employer may not dispose of your life as it sees fit. You are free to leave and go back to where you came from if you do not like the system, just as you were free to never sign on in the first place. You are not a slave at all in any manner. That's not an argument in favor of the backwards US immigration system, it's an argument that very, very clearly you are not a slave just because your job and visa are bound together. Immigration to N country is not a human right, it's a privilege (which is why I - and a billion other people - can't freely immigrate to Norway tomorrow and begin enjoying the associated perks).