Article continues below advertisementPrince William is bracing for a high-profile U.S. visit. Insiders tell OK! could ignite his long-running rift with Prince Harry, with the estranged brother's competing royal agendas threatening to collide on American soil.The Prince and Princess of Wales are expected to join King Charles, 77, and Queen Camilla, 78, for next year's celebrations marking the 250th anniversary of the signing of the U.S. Declaration of Independence.