Well CHI is being held in Europe this year, so apparently you don't!
But more seriously, the field is "HCI" everywhere, including in America, and has been for at least thirty years. I have vague memories of hearing the story about why the initial ACM SIGCHI folks didn't go with HCI at the time but I can't recall. Anyway, it wasn't long after CHI was founded that basically everyone was using "HCI" on both sides of the Atlantic.
Also it isn't "computer/human interaction." It is "conference for human and computer interaction."
If anyone is actually curious: The Association for Computing Machinery (ACM) started a Special Interest Group on Computer-Human Interaction (SIGCHI.org). Later, the Association for Information Systems (AIS) started a Special Interest Group on Human-Computer Interaction (SIGHCI.org) which has remained about an order of magnitude smaller in impact and comes from a different originating field (Information Systems). My impression is that nearly all the papers in one journal would also make sense in the other, but CHI sometimes has a little more design-y or consumer product stuff while IS-HCI has some stuff that's more from the perspective of an IT department.
The CHI folks can't unilaterally rename to SIGHCI without stomping over the smaller org, which means merging two different organizations, journals, and conferences run by different professional associations. Such a thing is occasionally proposed (e.g. http://www.bridginghci.org/wp-content/uploads/2018/03/chi-20...) which would be nice but in reality I think that's unlikely to happen because the cost exceeds the benefits.