The Western alphabet is used for abbreviations like WTO, NATO and so forth - but not for all. U.S.A. is written as "Bei Koku" in Kanji.
Ironically, that means "Rice Country"! XD
The letters are pronounced as in English - oa whatto za Japaneezu maydo ofu itto: WTO → "daburu yu ti ou"
And by the way, Japanese regard Romanji as exotic ... because the are no syllables :)
No L ...
The Japanese do not know L ... and they cannot pronounce it, they "shredder" it through their syllables and "translate" L to RU.
... You mix up with Chinese :) Japanese CANNOT pronounce L, even when they are drunk:
"Tanaka-san, say ´I LOVE YOU!´" - "Ai-rabu-yu!"