As the Copa America enters the knockout stage, the action on the pitch has been overshadowed by low attendances at several matches in the tournament being held in the United States, a potential concern two years before it hosts the World Cup.

Copa favourites such as reigning champions Argentina and Brazil advanced to the quarter-finals playing in sold out stadiums but the less heralded teams have played in half-empty arenas.

With the United States set to co-host the World Cup in 2026 with Mexico and Canada, swathes of empty seats are not a good look, with the Copa hosts themselves unable to fill up arenas for their group games.

The United States played Bolivia in their group opener at the 80,000-capacity AT&T Stadium but fewer than 48,000 fans turned up to watch the hosts win 2-0.

They failed to sell out their second game as well with 59,145 fans inside the 71,000-seat Mercedes-Benz Stadium while Arrowhead Stadium had scores of empty seats as the U.S. lost to Uruguay and crashed out of the tournament.

The same venues will also host World Cup matches in 2026, with the majority of the knockout games set to be played in the United States.

It is a stark contrast to the ongoing European Championship in Germany where matches have been played in packed arenas.

Games at the Euros averaged 50,000 spectators per game in the group stage.

But low attendance, especially for the U.S. games, cannot be attributed to a lack of interest as their final group game against Uruguay drew record television ratings with the largest audience to watch a non-World Cup soccer match.

MUTED ATMOSPHERE

South American soccer federation CONMEBOL, which is organising the tournament, said it had sold one million tickets by the close of the group stage.

But holding relatively low-key matches in massive NFL arenas instead of soccer stadiums has resulted in muted atmospheres at these games.

When Venezuela beat Ecuador 2-1 at the Levi's Stadium in California, only 29,864 fans turned up to fill the 68,500-capacity arena.

Sweltering conditions, which led to an assistant referee collapsing due to dehydration in hot and humid conditions in Kansas City, have not helped while sky-high ticket prices have kept fans away.

At the Euros, fans hoping to catch the quarter-final between Spain and Germany -- the 2010 and 2014 world champions -- could buy tickets for as low as 60 euros ($65) with European soccer's governing body UEFA handling ticket sales.

On the other hand, Copa America fans looking to watch quarter-final games - like Venezuela v Canada - will have to shell out a minimum of $110 on websites such as Ticketmaster and SeatGeek for the cheapest seats.

And unlike Germany, which is in the heart of Europe with all venues easily accessible, most fans hoping to follow their teams at the Copa would have to spend a small fortune on flight tickets.

CONMEBOL, however, added that it is on track to sell 1.5 million tickets by the end of the tournament, just as it did in the 2016 Centenario edition that was also held in the United States.