Got to remember that the Catholic Church is the LARGEST of the Christian Churches.
Osteen avoids political issues like the plague and talks about touchy-feely stuff that his dopey followers eat up, so having him address Congress would be pointless. Those who like hearing self-help "enpowerment" speeches would tune in, though.
Dobson isn't even a minister, he's a psychologist, radio talk show host and author. It would more akin to having Mark Levin address Congress. However, in both cases, I think their supporters WOULD tie up traffic for 4 days if Dobson or Levin was going to give a joint address to Congress.
A more apt protestant equivalent to the Pope would be Billy Graham his heyday. In fact, he's more akin to Pope John Paul II than Francis in that Graham was deeply revered and respected by non-protestant Christians. He absolutely would have gotten that kind of treatment if he addressed Congress.