LaLiga and Relevent Sports' plans to stage official games in North America suffered a damaging blow on Wednesday.
The Association of Spanish Footballers (AFE), including Real Madrid's Sergio Ramos and Barcelona's Sergio Busquets, met to discuss the issue and vowed to fight any decision to play a game Stateside, even threatening to go on strike.
"The players are outraged, very surprised and are all against it. It's unanimous," AFE president David Aganzo said. "The players don't want to play overseas.
"We are going to try to see that it doesn't reach that extreme [of a strike]. But we are willing to go right to the last option if it is necessary."
A meeting between AFE and LaLiga is scheduled for next month.
Last week, it was reported that there was "no chance in hell" of the initiative being approved by all the various stakeholders, including the United States Soccer Federation and Fifa.