John described the anti-Christ made up of a body of many members. Obama is just part of that body and plays a key role.
I John 4:3.
“And every spirit that confesseth not that Jesus Christ is come in the flesh is not of God and this is the spirit of anti-christ, whereof ye have heard that it should come; and even now slresdy is it in the world.”
If you interpret things that way, there have been billions of antichrists for 2009 years, which doesn’t make Obama very special in that regard—one in four billion antichrists.
Revelation is obviously talking about a singular person and sequence of events when it speaks of THE antichrist. So John’s “spirit of the antichrist” obviously refers to something different.