The problem has come about due to the tax fraud charge that the player received while he was at Barcelona, after he was judged to deprived the Spanish tax authorities of £885,000.
The Chilean accepted a suspended prison sentence as a result, and his now facing difficulties trying to attain a visa in the US.
His team-mates have already arrived in the country as they prepare to play their first match of the preseain in Arizona on Friday, and with several stars missing due to the World Cup the 'Red Devils' would love to have Sanchez with them.
The squad does contain some big names such as Anthony Martial, Juan Mata and Eric Bailly, but a lot of the team are unknown teenagers which will not help sell tickets to the games they have to play.
A proposed friendly against Milan at the 90,000 capacity Rose Bowl in Pasadena, California, has already been moved to a smaller 27,000 capacity venue as a result of the lack of interest in tickets.
It is also thought that the prices of the tickets is keeping American fans away from watching Jose Mourinho's men, but it is undoubted that former Arsenal winger Sanchez would add to the attraction of the matches.
While Man Utd's legal team are working hard to try and get the issue sorted, it is unclear when the Chile international will be able to fly out to join the tour.