I may be wrong but, do I detect a slight bit of anger?
China was an epicenter
Spain was an epicenter
Italy was an epicenter
People are limiting, "epicenter" to single countries, not groups.
At the moment, we have the steepest rate of infection. That is why people were saying we would become the epicenter.
At the moment, we have the most people of any country that has infections!
That is why people are saying we are now the epicenter, just like the numbers were showing.