This is an old topic. Some Americans get pissed off when foreigners comment on US politics especially in heated situation like election time.
Like others and I said before, the reason is that US policy affects in a more or less direct manner the rest of the world therefore election time is an occasion for those with no legal say in the matter to voice their opinions.
The perfect example for this are the Quebec election that took place yesterday. There was a 56.5% participation rate. My brother and I both canceled our votes because we weren't happy with any of the parties AND because we perceived the election as opportunism from the Premier Jean Charest. A reason given by the various analysis in the media, beside the sudden cold, is the election fatigue: we had to go through a Federal election, we followed closely the US election. And that is the point I wanted to make: a lot, if not most of the Quebecers, followed the US election. This fact was recognized by the Quebec's main electoral officer, Marcel Blanchet, who went out of his way making efforts to promote the vote: he opened additional days for the anticipation vote, send open letters to newspapers and used televised ads. So yes, for those wondering why Canadians, and others, post a lot regarding US policies, this is an example how deep US elections and politics affect us. I would have thought that it was a no brainer for people to realize that US foreign policy touches a lot of people, from neighbors to distant countries, especially when that policy leads to wars.