I simply disagree that's a strong brand worldwide because it's only a USA brand.

No one even said "strong brand worldwide" they said "one of the strongest brands in the world". Does a professional athlete have to compete overseas to be recognized as being exceptionally good at their sport, if they absolutely dominate in their home country, and their home country happens to be very significant in that sport? If you're going to get hung up on details, don't reword them.

Would someone who qualifies for the Olympics for the first time from a powerhouse country not qualify as "one of the best in the world"?

Walmart has stores everywhere but the North & South Poles. There's a reason they employ over 2.3 million people.