While I certainly take your point, that it's weird to have to register a party affiliation in a closed-primary state (assuming you live in one, and that you care to vote in the primary), and the range of political opinion in the news media is bizarrely closed, it's a mistake to confuse pseudo-official reflections of politics with politics itself, and to understate the lack of alternatives among the actual, you know, people.

There's no party here for me to vote for that reflects my politics, but voting here is always tactical, for a variety of unfortunate constitutional reasons. It's not clear to me, though, that the situation is significantly different in the UK or Canada. You can go for the CP in Ontario, but they don't have any seats in anything, so does it get you anywhere? It's even worse in the UK.