Her Majesty the Queen of Canada is our de jure head of state.
However, our de facto head would be Her Excellency The Right Honourable Michaëlle Jean, C.C., C.M.M., C.O.M., C.D., the Governor General of Canada. She represents Her Majesty in Canada, and the powers of the Government of Canada are exercised through her in the name of the Queen. The Governor General exercises these powers on the advice of the Queen's Privy Council for Canada (since the Cabinet is a committee of the Council). However, the advice of the Council is almost always expressed by the Prime Minister, exclusively, on important matters. The entire Council is only convened to proclaim new monarchs, under normal circumstances.
The democratic leader, our head of government, is The Right Honourable Stephen Harper, P.C., M.P., the Member for Calgary Southwest and the Prime Minister of Canada; he was invited by Her Excellency to form the government of the Thirty-ninth Parliament of Canada as the party most likely to have the support of the House of Commons, and he was sworn in as the Prime Minister on the 6th of February of this year (Mr. Harper is the Leader of the Conservative Party of Canada).
Major parties in Canada are the Conservative Party of Canada (the present Government), the Liberal Party of Canada (serving as Her Majesty's Loyal Opposition, a position often thought to be the alternative to the current Government in the event that the Government resigns), the Bloc Québécois (a sovereigntist party from the Province of Québec), and the New Democratic Party of Canada.
Canada has various Presidents, but these are not sources of any major power when compared to the head of government or the head of state (the President of the Treasury Board, or the President of the Privy Council). However, the power in Canada rests greatly on the Prime Minister, who is trusted to make appropriate and responsible appointments to the highest positions in the Government of Canada and the judiciary (although the "appropriate-ness" of these appointments has been a point of contention in more recent years).
Yes, Canada and the United States of America share views on certain topics, and diverge on others. Canada has agreed much more with the United States since Her Excellency invited the Conservative Party to govern; the relationship with our southern neighbour was considerably more "turbulent" under the longer tenure of the Liberals.