Western countries; European and North American countries
Refers collectively to the nations of Europe and North America, often in political, economic, or cultural contexts.
In Western countries, there is a tendency to emphasize individual rights.
This product was developed for European and North American markets.
欧米 is a shorter term for Europe and America, while 欧米諸国 explicitly means 'Western countries' as a collective noun.
西洋諸国 is a broader term for Western nations, sometimes including Australia and New Zealand, whereas 欧米諸国 specifically refers to Europe and North America.
Compound of 欧 (Europe), 米 (America), and 諸国 (various countries).