C19study's affiliate website / white paper, hcqmeta.com, has actually run the numbers on a related statistic:With late treatment, or used alone, it's still likely to be somewhat effective, except when used in studies funded by major Western pharma companies.
Figure 9 shows the results by region of the world, for all regions that have > 5 studies. Studies from North America are significantly more likely to report negative results than studies from the rest of the world combined, two-tailed z test -3.09, p = 0.002. [Berry] performed an independent analysis which also showed bias toward negative results for US-based research.
It's intriguing that Europe shows far less bias than North America in its scientific research. As far as I know, European mainstream press coverage is equally negative, and European doctors are generally just as unlikely to prescribe.