Yes I know this is a quite provocative question.
First a disclaimer: I've been working on Wikitree for less than three months, but quite actively (2000+ contributions to date), and although I'm not American I enjoy it.
I've tried to bring in a few family members, and a couple of friends involved in genealogy. All of them French, as myself, some having "their" tree managed in Geneanet, mainly. None having interest in DNA genealogy, AFAIK. Their main objection to joining WikiTree boils down to : too much American stuff : interface language of course (but that's not I think critical), but underlying spirit, so to speak, and data model. How a data model could be culturally biased? It's always so. Ask anyone who was involved in data migration in companies merging how a data model conveys the enterprise culture, and what pain it is to merge them. I won't enter into details here, but obvious examples are the various fields for "name". "Middle name" among others, makes absolutely no sense for a French.
I tell them : come on, the best way to have WikiTree look less American is to have more non-American on board. But that does not really work. And it's too bad because we have here in France a lot of serious genealogists, and a wealth of solid archives ready to be added to WT.
This is a real issue, because the written mission (which I buy 100%) is to build a single family tree for all of us. It would be too bad to give the impression that this "us" stands for "US" and not "we, the humans".
Of course there are "projects" for non-American coordination (France, Netherlands, Germany, Australia etc) but they look like sort of extensions of the WikiTree core, which stands firmly American.
I'm willing to work on this issue with interested people. There is certainly no silver bullet. This post is just to make sure other people here are aware of the issue and willing to work towards solutions.
Thanks for your attention.