In the US, it seems like malpractice to teach anything before Spanish IMO. 14% of the country are native Spanish speakers. It's hard to imagine a return on any other foreign-language instruction that would match improving communication between 45 million residents of the country and everyone else, to say nothing of improving communication with citizens of the other countries actually sharing a land mass with the US.
Learning Spanish in school was the single biggest waste of time. 14% of the country are native Spanish speaker! Many professions require some spanish! Those were the arguments back then as well.
However... unless you account that the native speakers and heritage speakers will learn English, making your ability to say cerveza useless. If you aren't fluent and have professional Spanish qualities (like Medical Spanish), its useless. Learning Latin or Greek would have been more useful, at least I could struggle through Cicero in Latin, than saying 3 words in Spanish before the other guy switches to English.
If we find a way to make 4-6 years of language instruction reliably lead to a reasonable level of language competency, maybe. But until then, the student's underlying interest in the language is much more important than any abstract sense of usefulness. I took Spanish in highschool, and despite being moderately ambitious about it, never got very good, and never got much use out of it, despite living in Florida and Texas. I suspect (although alternate history is hard, so I can't guarantee) that I would have gotten a lot more out of Japanese, simply due to alignment of interest.
If you extend that logic to the world, is it malpractice to teach anything before Mandarin or Hindi?
No, because native Mandarin speakers make up only 1% of American citizens.
In the US you are very likely, at some point in your life, to encounter native Spanish speakers with poor English competency. Outside of higher education, you are very unlikely to encounter native Mandarin speakers with poor English competency.
... I'm not sure what part of "If you extend that logic to the world" you didn't understand.
The logic is inherently local.
The typical student does not emigrate or even travel that much, so you don't prepare them to encounter a human randomly selected from the population of the Earth, you prepare them to encounter a human randomly selected from the regions where they are likely to spend their lives.