The fixture between Ulsan HD and Mamelodi Sundowns was by far the worst attended match.
Stadiums have been 56.8% full, with more than half a million (556,369) spectators attending.
Nine stadiums have been used for the first 16 matches of the tournament, with a combined capacity of 979,373.
The expanded tournament is being treated as a dress rehearsal for the international men’s World Cup next summer, which will be held in the USA, Canada and Mexico.
Of the 16 matches played so far, half of the matches have seen attendances below 50% of the capacity of the stadium.
The lowest attended game was South Africa’s Mamelodi Sundowns win over South Korean side Ulsan HD in front of 3,412 spectators at Inter & Co Stadium in Florida.
The fixture between Ulsan HD and Mamelodi Sundowns was by far the worst attended match.
The official attendance meant the stadium was just 13.6% full.
The stadium for River Plate’s win over Japanese club Urawa Red Diamonds was 17% full, while it was 20% for Salzburg’s win over Pachuca in Cincinnati.
Only 31% of the capacity of Atlanta’s Mercedes-Benz Stadium saw Chelsea beat LAFC in their opening match.
Despite the setbacks, Fifa is optimistic that attendances will increase. In a statement on Tuesday, it said that “four of the five top-selling group stage matches are still to come”.
Fifa says nearly 1.5m tickets have been sold for the tournament and despite the issues there have still been some large attendances.
The highest-recorded crowd of 80,619 watched Paris St-Germain’s 4-0 win over Atletico Madrid at the Rose Bowl Stadium in California.
The three matches in Miami, which has a large Hispanic and Latino population, have been highly attended. Fifa said the opening game between Inter Miami and Al-Ahly was watched by 60,927.
Boca Juniors’ Group C match against Benfica had more than 55,000 in the 65,000-capacity Hard Rock Stadium.
The third game in Miami had 62,415 attend Real Madrid’s 1-1 draw with Saudi Arabian side Al-Hilal.
Inter Miami and Boca Juniors are playing in Miami again later in the group stage.
