You are talking utter nonesense, Wilder isn't the lineal champ, he's not the only champ in the division, he's A champ, Joshua is also a champ who holds more belts and is a significantly bigger draw. AJ has just got out of a meaningful, top level Heavyweight title contest, he's the one acting like a champion, he won the belt and then unified it after 1 defense against the long reigining champion. Wilder beat up Gerald Washington.
Joshua will likely beat up Klitschko next then the fight will be readily available for Wilder. If AJ wants to fight in Vegas, it might happen in America, but the likely scneario is that the guy with all the money and more of the belts decides to fight in Wembley. At that point, Wilder would be ducking AJ if he refused to fight him. When you earn what Wilder does and have a resume like he does, you are in no position to demand that someone like Joshua comes to you, which is exaclty why he will do as he's told and cross the water.
Everything you say about what AJ is doing to avoid THE CHAMP could also be said about Wilder..avoiding THE CHAMP.