For example your blog is going to be about the automobile industry you will find that the word car is more popular than auto in the US. However auto is more popular internationally. So even if you normally use the word auto using the word car for a US only site would be a better word choice.
The key is to know your audience before you start addressing them. Have you ever talked with someone who really knew what they were talking about, but you didn’t understand a word they said? Don’t let your readers feel this way about you! Write to them in their language.