A growing number of the cars Japanese brands sell in the United States are made in Mexico, and the country's production base is growing nearly as fast as China's, NBC News reported.

Toyota, the world's largest automaker, this month announced plans to build its first major assembly plant south of the border, the network added. The $1 billion investment is part of a "strategic re-thinking of how and where we build our products," noted Jim Lentz, the company's North American CEO.

Last month, Germany's Volkswagen said it would invest that same amount into its sprawling assembly complex in Puebla, about two hours from Mexico City. And Ford is set to soon announce a $2.5 billion investment to boost the capacity of its various Mexican operations, which include two assembly lines and an engine plant, NBC News detailed.

Today, Mexico calls itself the leader in automobile production across all of Latin America, Economía Hoy noted, having left behind crisis-ridden Brazil, where both car production and sales further slumped last month.

In 2014, some 3.3 million vehicles were made in Mexico, which turns the country into the seventh largest auto producer in the world, data collected by the International Organization of Motor Vehicle Manufacturers showed. Even more encouraging is that the level of production rose by 10.2 percent, compared with the previous year.

And Eduardo Solís, the president of Mexican Automobile Industry Association, could not be happier.

"The growth in production and in exports has been spectacular," Solís beamed, according to NBC News. "The growth reflects the confidence the industry has in our country," he added.

But not everybody is seeing the record production is such a positive light: Dennis Williams, the president of the United Auto Workers, charged that companies building in Mexico are taking advantage of "slave-like" wages, CBS News noted.

Instead of moving production to Mexico, U.S. automakers should up their local investments, the union demanded.

"American manufacturing workers could have had good-paying jobs that respect basic human dignity," Williams insisted.

Automakers, though, note that they also poured $46 billion into improving American factories in the past four years.