I thought also because COTA was a proper facility and they didn't want multiple US rounds because the crowds were light, also because of Argentina. They had enough coverage for North and South America each having a race.
Thing is they do not remotely care about the crowds at the track. They get paid no matter what. They care somewhat about the scheduling - the teams at least do - and they care about getting paid the sanction fee. They're a business, they aren't in this because of just love of the sport.