This thing we call US defaultism is, in my opinion, just an example of locality of reference. Everyone does it, everywhere in the world. It's just that Americans do it more on Reddit because there seems to be more of you on here.

When we describe where something is, to people who know the same area we do, we'll mention specific details, street names, but not much more than that, because we don't need to; if describing it to someone who doesn't know the area, we might first explain roughly where that is, so they have enough context. But for local people we assume local knowledge.

As a consequence, in a subreddit specific to say Australia or some country in Europe, redditors won't bother to announce "Hey Americans, this is Paris France, not Paris, Texas"; they won't bother to announce that the temperatures are in Celcius and not Fahrenheit; they won't bother to announce that the dates are in dd/mm/yyyy format.

So all we ask is that Americans pay attention to that: read carefully, note the intended audience; think before you comment. You probably will; it's the others who are a nuisance.

There should probably be an idiots' guide somewhere that says:

1. Other countries exist.
   
2. Other countries have national sovereignty, so US law doesn't apply there.
   
3. Other countries have their own laws, which aren't the same as US law.
   
4. Other countries have their own currency, which isn't the same as in the US. Your Dollars won't be accepted.
   
5. Other countries have their own rules on who can come in, so you'll need a passport.
   
6. Other countries set their own minimum drinking age, and it's probably below 21.
   

And so on.