This is a weird conversation.
For starters, Joel Embiid played basketball for one year of his life and then moved to the US. The US produced him, for all intents and purposes.
People talking about Kevin Durant, bigs shooting threes, etc. is funny because European bigs were largely the first players to bring that style. Remember Dirk Nowitzki? It's not that Americans developed a new playing style for bigs and the Europeans have stuck to a traditional model--the foreign players are the ones who largely introduced a more well-rounded offensive style to big man play.
The real answer is that basketball is becoming more globally popular, and more people play basketball outside the United States, so outside-the-US players make up a higher percentage of the world's best players than they did in prior generations. This is especially true for big men, given that the requirement to be a good big man in the NBA starts with you being in the 0.000001% height percentile. The odds are that people in that height percentile are NOT going to be from the United States.
There is a reason most foreign-born players tend to be big men. Just like there is a reason most players who tend to play past 35 are big men. There is just a real shortage of people that can meet the physical requirements necessary to play at an elite level, and if you fit that profile, there are scouts all over the world trying to find you.
Basketball is a global game, played by millions of people, but unlike soccer, baseball, track, or other sports, it's incredibly selective on the physical dimensions a person needs to have to play at an elite level. It's a real genetic lottery, and that means that good players can come from anywhere, with some countries producing more than others.
One of the most interesting things that took place in the FIBA Championships was South Sudan handily beating China. China has spent billions of dollars to try and become a basketball power, and yet they were easily defeated by one of the poorest countries in the world. That happened largely because despite it's massive population, the Chinese people are not particularly physically suited to play basketball. On the flip side, it's the perfect game for the people of South Sudan.
