Almost all ML research is published on arXiv.

In ML (as in most of Comp Sci) conference proceedings (NeurIPS, ICML etc) are where the prestige publishing is.

I can't speak specifically to this topical domain, but generally speaking (assuming the research topic isn't politically sensitive) there are professional incentives to do transnational work -- whether it's publishing in Anglophone journals, organizing international conferences, etc. So probably, it's not that foreign journals are valued less. (Probably, in fact, the contrary.)

Perhaps their papers are disproportionately not accepted to conferences so we see many more on arXiv