LaMelo Ball's stint in Lithuania has made him INELIGIBLE for one of the biggest honors at the high school level -- the McDonald's All-American Game ... officials tell TMZ Sports.

The All-American game features the top 24 players from around the country selected by a voting committee based on their athletic and academic success.

Superstars from Magic Johnson to LeBron James to Kevin Durant to Melo's older brother, Lonzo?, have participated in the game -- being selected to the team is one of the highest honors a high school player can have. 

Of course, Melo announced his return to prep hoops earlier this week by enrolling in elite Spire Academy private school in Geneva, Ohio ... bringing him back to amateur status.