@jayballer73
Other than the US, most of the countries in the Americas do not have well developed high school programs, which means their U18 and lower teams are often under-developed. Here in the US, because we have a robust HS program, it is very easy to identify the best HS players in the country (and we have lots of them).
USA has never lost a game in the U16 competition (closest game last year was a 41 point win). The team shot almost 57% from the field for the tournament. RJ Hampton, Jalen Green and Vernon Carey are some names you would recognize from that roster.
The USA U17 team is 30-0 at the World Championships. They will be playing in a couple of weeks in Argentina. Vernon Carey, RJ Hampton, and Jalen Green will likely be on that team this year, although training camp starts today with a roster of 30 that has to get cut down to 12, so that's not guaranteed. Still, the US has never lost at the U17 level.
The U18 team is 53-2 at the Americas Cup, losing in the semifinal in 2002, and the title game in 2008.
The U19 team is 91-14 all time.
You see the difference. Undefeated at the U16 and U17 levels. Only a couple of losses (and never prior to the semifinal) at the U18 level. A crazy winning percentage (.866) at the U19 level, but compared to undefeated or .963, that's a substantial drop. Basically goes from no chance to a snowball's chance in hell, to maybe you have a shot. Most countries don't have enough talent at the lower levels, so they play their best younger players up. A guy like Svi, who played on the U16 Ukranian team in 2013, then played for the senior national team in the 2014 basketball World Cup, then the U20 team in 2016. That's the equivalent of a guy like Lebron James making the national team as a high school junior in 2002. That would probably never happen here in the US. Just too much talent ahead of him to even consider a player like that.