Postby Airth » March 10th, 2007 6:15 am
If you try 米国 and search for Japanese pages only it returns 7,640,000 hits. Compare that to a Japanese only search for アメリカ of 9,860,000. Almost the same. If it were possible to search for 米 by itself without picking up all the rice that's out there, you would find the kanji is actually used more than the Katakana (on the internet anyway).
Doing the same thing for the UK: イギリス = 7,210,000 / 英国 = 3,750,000 (and let's not get started on whether or not we're talking about England or Britain). Again, as with 米 we can't get a true figure for 英 when it's used alone as an abbreviation.
To answer the original query; stick with メキシコ, however sexy 墨西哥 looks. I showed those kanji to my (Japanese) wife and she just laughed saying it was the first time she'd seen them. In general, there aren't that many countries that are written with kanji, and when they are it's usually for the sake of saving space. In other words, you'll mainly come across them in newspapers, official documents, or the other place that comes to mind - on the signboard for NOVA.