So garlic grown somewhere in the USA, but not necessarily California, is no good? It has to be California garlic only?
Or do you mean to advise that China-sourced garlic may be impure or dangerously treated, but garlic grown here in the USA may be a safer choice?
Also, all food imported into the USA is sampled and tested in FDA laboratories to screen for dangerous impurities, infestations, or other unwholesome attributes. Imports are stopped if random testing does not meet quality standards. Perhaps some slips through, but not often and not for long.
I don't disagree that China may be lax in its release of some contaminants, but I do not believe that 80% of the world's garlic is toxic because it's grown in and exported from China.
I did some research and found the advisory words you posted were verbatim from a report online from a source called Boredom Therapy! Perhaps that is for people preoccupied with alarmist advice to offset boredom?
https://boredomtherapy.com/american-garlic-vs-chinese-garlic/