I only see the hill article using that parlance. I looked at the articles the hill certainly says half the country voted for Trump. It is an opinion piece you linked to though not a news piece.
The center for politics and global citizen articles do not seem to use half that way though.
For center for politics the title starts with "How the Other Half Votes" and they seem to keep to that usage and never use half of USA/America.
For Global Citizen the title starts with "Half the Planet Will Vote This Year" an they seem to stick to that and never use half of USA/America
I intentionally linked to variations on that wording to show there's a pattern. If you're looking for those exact words, you can find plenty more examples online.
I do not see the pattern you are seeing. What I would need to change my mind here are communities using the parlance correctly, understanding the meaning, and it not leading to misunderstandings to a reasonable percent of the community.
The center for politics and global citizen articles do not seem to use half that way though.
For center for politics the title starts with "How the Other Half Votes" and they seem to keep to that usage and never use half of USA/America.
For Global Citizen the title starts with "Half the Planet Will Vote This Year" an they seem to stick to that and never use half of USA/America