Interesting -- it had never occurred to me that the French word for улица, namely rue, might sound a little bit like the слово из трех букв, to a Russian's ears!

Technically, the "R" sound in rue is voiced, and so it must sound closer to the г in Господи or не дай Бог, than to the sound х. But I suppose that in some contexts (к примеру, когда шепчешь), the "R" in rue would be voiceless... and therefore the word would sound "funny" to Russians!
French "r" is voiced and does not sound like "x". "Rue" does not resemble "хуй" at all. The vowel is also different and there is no any й in "rue". Господи is usually pronounced with "г" in Northern Russia (in Moscow too). Бог is pronounced like бох. Voiced consonants cannot appear at the end of words.