Custom Shape Maps Unexpected Error

I can find lots of threads where people have this problem, but I can't find one with an actual solution. All I see is people insisting that it works, but it definitely does not work.

When I try to load any custom shape map, such as any of these provided by deldersveld I get an "Unexpected Error" message. The details say "Failed to execute 'btoa'". In other threads some people can load these files and others can't. deldersveld says it's a "regional issue" but I don't really know what that means, and I haven't seen anyone offer a way to fix this "regional issue." Does that mean that custom maps just don't work for people who live in certain regions? I find that unbelievable. I am using the latest release of Power BI Desktop, and I am in the United States.

I know shape maps are still technically in preview but surely if it works for some people it should work for everyone. Is there seriously no way to fix this? How do I load a custom shape map? Specifically I need a world map of countries.