"China and Vietnam are Asian countries."
Translation:La Chine et le Vietnam sont des pays asiatiques.
Why? For God's sake, why, are two nations "La" and "le"? Why can't they and all nations be one gender?
Names of countries have a grammatical gender too, but fortunately it tends to be predictable: all names that end in -e are feminine (la France, la Chine, la Russie, la Belgique...) with very few exceptions (le Mexique, le Mozambique, le Zimbabwe), and the others are masculine (le Canada, le Honduras, le Vietnam, le Monténégro...) (but note that the majority of country names end in -e and are thus feminine). This also applies to names of states, regions, islands, etc.
The grammatical gender of a country is important, because different prepositions are used depending on it: for instance "in China" is "en Chine", but "in Vietnam" is "au Vietnam"
Note finally that a small number of countries are not used with an article:
usually island nations and other small countries: for instance Cuba, Monaco, Israël, Malte, Singapour...
These countries use the preposition à for in/on, except Israël which uses en: à Cuba / à Monaco / en Israël / à Malte...
I think where people go wrong is in thinking that any language (apart from possibly Esperanto) is logical.
It's a natural assumption when learning a new language, especially when you don't have to think of the numerous quirks of your own.
I agree it would be nice, though. I just cling to the one rule that seems fairly constant (while I rock myself to sleep): french words ending in -tion are generally feminine.