Well this article explains that, yes, it is considered dangerous and some police forces in the US had already banned it. Look at this figure:
Since the beginning of 2015, officers from the Minneapolis Police Department have rendered people unconscious with neck restraints 44 times, according to an NBC News analysis of police records. Several police experts said that number appears to be unusually high.Minneapolis police used neck restraints at least 237 times during that span, and in 16 percent of the incidents the suspects and other individuals lost consciousness, the department's use-of-force records show. A lack of publicly available use-of-force data from other departments makes it difficult to compare Minneapolis to other cities of the same or any size....
More than a dozen police officials and law enforcement experts told NBC News that the particular tactic Chauvin used — kneeling on a suspect's neck — is neither taught nor sanctioned by any police agency. A Minneapolis city official told NBC News Chauvin's tactic is not permitted by the Minneapolis police department. For most major police departments, variations of neck restraints, known as chokeholds, are highly restricted — if not banned outright.This article goes into more detail on how a few different cities' police forces across the nation have dealt with the tactic.
The version of the Minneapolis Police Department's policy manual that is available on-line, however, does permit the use of neck restraints that can render suspects unconscious, and the protocol for their use has not been updated for more than eight years.
It seems pretty ridiculous that there is such a lack of uniformity across the nation on this, for so long too.