The European champions head into next month's tournament among the favourites, with De la Fuente's 26-man squad built around eight Barcelona players and none from the Spanish capital's biggest club, bringing the fierce El Clasico rivalry into the national team's debate.
Defenders Dean Huijsen and Dani Carvajal were among the Real Madrid names to miss out on a team chasing Spain's second World Cup title after their 2010 triumph in South Africa.
De la Fuente dismissed the idea that the decision could cost him support among Real Madrid fans.
"For me, the greatest team there is - the very greatest - is the Spanish national team," De la Fuente said during a breakfast with media representatives organised by Spanish public broadcaster RTVE and news agency EFE.
"I don't look at where players come from or their background. What matters are Spanish players who are proud to represent their country's national team and to be part of a united nation."
Yamal 'raring to go' as he recovers from injury
Barcelona's contingent comprises Joan Garcia, Pau Cubarsi, Eric Garcia, Gavi, Pedri, Dani Olmo, Lamine Yamal and Ferran Torres, while seven players called up are based in the Premier League.
The manager said sporting considerations alone guided his selection, even if squad decisions inevitably carried a subjective element.
"The day I make a mistake, fail to make the right choice, or act in a way that might be beneficial just to get a result, I'm putting my job on the line," he said.
Spain open Group H against Cape Verde before facing Saudi Arabia and Uruguay, but De la Fuente may yet take a cautious approach with Lamine Yamal, Nico Williams and Mikel Merino, who are all recovering from fitness concerns.
"We're in contact with all the clubs," he said. "We know that these players are in good physical shape; each one is making good progress in their recovery process. I'm very optimistic; I think they'll be available for the first match."
Still, De la Fuente said Spain's view stretched beyond the opener.
"If we have to take a risk, mate, we'll take it in a World Cup," he said. "But... our view goes beyond the first match and also the second. So, if we have to wait a little longer, we'll wait."
On Yamal, the 18-year-old Barcelona winger expected to carry much of Spain's attacking threat, De la Fuente said youth had not dimmed his sense of occasion.
"Yamal is absolutely thrilled and raring to go," he said. "He's a very young lad, just 18, but he has a remarkable sense of maturity and knows that this is his moment.
"You have to seize the moment. And he knows this is his moment."