>I'm trying to understand how the political system of the US work and I need your help to clear the things up.
>
>For comparison, here in Canada, the political leader of a party is choosen by the (paying) members of the party. We don't vote for a delegate, we vote directly for the leader of our choice. As I understood it, in the US you vote for a delegate that will vote for you. Why is this? Why can't you vote directly for Clinton, Obama or McCain for exemple?

We have an very aniquated system called the 'Electoral College' which was created because our founding fathers did not trust the 'everyday man' to be able to make informed choices in elections, given the size of the country and lack of communication.
The primaries are designed (and it has been awhile since I had Government classes, so I might be a little shadey here) to 'assign' delegates to the candidate chosen by majority vote (although some primaries are assigned by percentage, depending on the state). These delegates go to the party conventions and cast their votes for a particular candidate, until one candidate has the required votes to become that party's official candidate. So what we have going on now is the 'election to have a chance to be elected'. Once the party conventions are over, then the 'real' electioneering starts.


>
>In the US, the vote for the presidency is spread accross many weeks.

The actual vote for presidency is one day. Everything else before is dancing for position.

"the vote is done in one day. More than that, it take into account the different time zones and try to hide the results of the eastern provinces to the western provinces until the western provinces poll boots closes"

On election day, this is exactly what is supposed to happen

>
>Here we have 4 parties who share the power in the parliament. The US seem to have only 2 parties (Democrats and Republicans). Why only 2? Is it in the Constitution?

There is no Constitutional rule that requires any party at all. We seemed to have settled on 2 major parties, although throughout our history we've had more. And even today, there's the Democrats, the Republicans, the Libertarians, the Green Party....and proabably several more that I'm forgetting right at the moment.
>
>In the US, it seem that you vote once for the president and once for the parties. That's a good thing IMHO. Here we can only vote for a party in a general election. The leader of that party is automatically named the Prime Minister. I also like very much the law that limit the number of mandates to

We don't necessarily vote for a party, although you can do what's called 'straight ticket' voting, where you, in essence, say "I'm voting for anyone who's a (fill in party here)


2. I whish that this law could be adopted here in Canada.



Hope this helps, tho' I doubt it - the whole system could stand an overhaul, but we're just not sure how to do it.