Ivica Olic looks to be on his way back to Hamburg, with Andre Schurrle increasingly likely to join Wolfsburg.
The Potters have a deal in place for the Houston Dynamo defender but are still waiting on international clearance.
It is unlikely that Cameron will be given the green light by the time Tony Pulis' side return to England from their pre-season tour of the United States.
They are, however, optimistic regarding their chances of getting the deal signed off well before the start of the new Premier League season.
"We wouldn't have come this far and worked as hard on getting the deal done if we didn't think we had a good chance of getting a work permit," chief executive Tony Scholes told the club's official website.
"Ideally, he would have had more international caps, which would have made it easier. But the fact that he is a first choice in the US national side will count in his favour.
"Ironically, two other important factors are the difficulty in getting the deal done, because the MLS didn't want to lose one of their best players, and the move by another Premier League club to come in for him and make it difficult right at the end of the negotiations.
"It should also work in our favour that Geoff has been in the MLS All Stars XI three times in the past five seasons, voted by his peers as one of the best. In those other two seasons when he wasn't selected, one was his rookie year and the other he was injured."