The U.S. men’s basketball team is not unbeatable. Perhaps a loss at the 2024 Paris Olympics is unlikely with LeBron James, Steph Curry, Kevin Durant and multiple other All-Stars. But not impossible.
The U.S. lost to France at the 2020 Tokyo Olympics (but still won gold), and the Americans did not medal at the 2023 FIBA World Cup.
Of the 11 other teams at the Summer Games, a few — Germany, Canada, Serbia, Australia — can beat the U.S. in a one-game scenario playing a 40-minute game under FIBA rules (slightly different than the NBA game) against teams with more continuity.