I am often asked about my “accent”. The most common guess is that it’s a “British” accent, while I lived in London for about a year I don’t think that my accent changed much during that time (people have commented on the way I speak since I was in primary school). Also there isn’t a “British accent” anyway, the Wikipedia page of Regional Accents of English has the first three sections devoted to accents in the island of Britain (and Northern Ireland is part of the United Kingdom which people often mean when they sat “Britain”). The Received Pronounciation is the main BBC accent and the accent that is most associated with Britain/England/the UK (which are three different things even though most people don’t know it) and I don’t think that I sound like that at all.
I’ve had various other guesses, the Netherlands (where I lived for a few years but mostly spoke to other foreigners), New Zealand (which I’ve visited a couple of times for conferences), Denmark (the closest I got was attending a conference in Sweden), and probably others I can’t remember.
If I actually had developed an accent from another country then it would probably be from the US. The amount of time I’ve spent watching Hollywood movies and watching US TV shows greatly exceeds the amount of time I’ve spent listening to people from all other countries. The fact that among all the people who wanted to try and guess where my accent supposedly originated none have ever included the US seems like strong evidence to suggest that I don’t have any sort of accent that really derives from another country. Also I have never had someone mistake me for being a resident of their own country based on accent which seems like clear evidence that all claims about me having a foreign accent are bogus.
Autism forums such as WrongPlanet.net  always turn up plenty of results for a search on “accent”. In such discussions it seems that a “British accent” is most common mistake and there are often theories raised about why that is – often related to speaking in a formal or precise way or by using a large vocabulary. Also in such discussions the list of countries that people supposedly have accents from is very inclusive, it seems that any country that the listener has heard of but doesn’t know that well is a good candidate. The fact that Aspies from outside the US are rarely regarded as having an American accent could be due to the fact that Hollywood has made most of the world population aware of what most American accents sound like.
Also if I really had some sort of accent from another country then probably someone would comment on that when I’m outside Australia. When I’m travelling people tend to recognise my accent as Australian, while it doesn’t please me when someone thinks that I sound like Crocodile Dundee (as happened in the Netherlands) it might not be entirely inaccurate.
This is Annoying
The way the issue of accent is raised is generally in the form of people asking where I’m from, it seems to imply that they don’t think I belong in Australia because of the way I speak. It’s particularly annoying when people seem unable to realise that they are being obnoxious after the first wrong guess. When I reply “no” to the first “are you from $COUNTRY” question and don’t offer any further commentary it’s not an invitation to play 20 questions regarding where I’m supposedly from, it’s actually an indication that I’m not interested in a conversation on that topic. A Social Skills 101 course would include teaching people that when someone uses one-word answers to your questions it usually means that they either don’t like your questions or don’t want to talk to you.
Social Skills vs Status
The combination of persistence and misreading a social situation which are involved when someone interrogates me about my supposed accent are both parts of the diagnostic criteria for Autism. But I generally don’t get questions about my “accent” in situations where there are many Aspies (IE anything related to the Free Software community). I think that this is because my interactions with people in the Free Software community are based around work (with HR rules against being a jerk) and community events where no-one would doubt that I belong.
I mostly get questions about my “accent” from random middle-class white people who feel entitled to query other people about their status who I meet in situations where there is nothing restraining them from being a jerk. For example random people I meet on public transport.