[628C6l0]

That's true, but I think the full name usually has, just as the full names of Beijing Shanghai Tianjin etc contain 市 even though the short names doesn't.

And the short names of England, France, America, Germany, Korea, Thai, and China itself contain 国. This seems to suggest that there was a naming convention initially being followed.

Better examples than country names for illustrating this difference between Chinese and English include disease names (mentioned above), fish names, bird names, tree names, flower names, mountain names, river names …