Just to be clear: do not say anything like that! It is complicated. It is certainly "bad language." However, someone who says something like that is not really thinking about Jesus, or about the literal act, so it is not exactly an insult to Jesus. It is "bad language" to misuse religious words. (The word "profanity" means "misusing religious words.") But someone who says "God dammit" is not really thinking about God, he is just showing that he is so angry that he is forgetting to control his speech. The F-word is also bad language, possibly the most taboo word of all. But, again, when it is used to express anger, people are not really imagining the literal act. Again, it means "I am so angry that I am not controlling my speech." Some people just sprinkle it here and there in their conversation, fairly casually, as an intensifier. If someone is used to doing that everywhere else, they will use it to intensify other bad language. If someone is used to saying "Get your f---ing dishes out of the f---ing sink," they might well say "Fa crisake, get your f---ing dishes out of the goddam sink!" They are not really thinking about sex or religion, they are just using bad language to shock people.

Yes and no. People that are religious will say that yes it is directly offensive to God as it is "taking the Lord's name in vain" or "using God's name in anger". Other people that are not religious would consider that this is merely offensive language, but not offensive to God directly.

In Canada, it is offensive to most people. People who routinely say s*t, s*k, and f*k are normally considered "uncouth." These words have traditionally been associated with the coarse speech of criminals and unskilled workers. Counterculture music such as punk and rap have adopted these words as "protest" against the main society and the words are "fashionable" with some young people. I understand that in Britain, these words are fairly common and aren't as offensive as they are in Canada.