Think of it this way: a good practicing/worshiping Muslim who does good in his life has nothing to fear. For, he is 1 year closer to possible death and 1 year closer to Allah(s.w.t.). Congratulating somebody on their birthday has no religious significance. It is the same as congratulating somebody who just gave birth, finished graduate or medical school, just graduated college. It is a mere form of showing somebody that you are proud of their accomplishments. Doing the exact opposite of something people in the west do because they contradict your principles, or whatever, is incredibly foolish. Would you not go to school, or university, just because people in the west do it too? Let's remember one important thing, the Qur'an is for all periods of time. Meaning, everything in the Qur'an applies to every situation in any point in time. If something is said to be haraam in Qur'an, then it is absolutely haraam, since the Qur'an is the absolute word of Allah. If it is not mentioned to be haraam in the Qur'an, then what is the point of saying something is haraam?