From the WSJ:

For decades, minor-league rosters seemed the essence of America’s heartland. But thanks to growing numbers of foreign players like Mr. Lee, the minors are fast turning into a veritable United Nations. . . .

No surprise who’s responsible:

The surge of young foreign players into the U.S. minor leagues began in 2007, a few months after then-president and former major-league team owner George W. Bush signed the Creating Opportunities for Minor League Professionals, Entertainers and Teams Act, known as the Compete Act. It freed the farm systems of major-league teams from having to compete with all U.S. employers seeking H2B work visas for foreign employees, the supply of which usually was exhausted each year by February. Now, teams can import as many prospects as they want. . . .
The changes pose a challenge to American teens hoping to make the big leagues. Instead of signing hundreds of U.S. amateurs out of high school — the traditional business model for stocking minor-league rosters — teams are drafting fewer U.S. kids and signing more so-called nondraft free agents, the vast majority of them teenagers from Latin America.

And yes, it’s all about cheap labor:

Economics plays a huge role. U.S.-born players drafted out of high school rarely sign a contract to turn pro without a cash bonus, most in excess of $100,000. This summer, the Cubs have forked out more than $6 million in signing bonuses to 26 U.S. prospects, an average of nearly a quarter million apiece.
While some foreign players like Mr. Lee got hefty signing bonuses, the majority do not. Latin players in particular can be had for a lot less — just $10,000 in the case of Venezuelan pitcher Eduardo Figueroa, one of Mr. Lee’s teammates. Third baseman George Matheus, another Hawk from Venezuela, received $15,000 for signing.

A new report out today breaks out the immigrant share of 465 civilian occupations tracked by the Census Bureau (baseball players are not listed separately but lumped in “Entertainers & Performers, Sports & Related Workers”). The punchline is that there are only four small occupations that are majority immigrant (legal and illegal), and even there nearly half of workers are native-born. The native-born dominate occupations people imagine as immigrant-dominated, like maids and housekeepers (55 percent native-born), grounds maintenance workers (65 percent), janitors (75 percent), et al. Whether a particular business has a problem finding help is not the government’s problem; but to argue that large federal immigration program is needed because Americans are unwilling or unable to do these jobs is simply laughable.