That doesnt help. You have to be a leader to lead a country. I dont think even Manmohan Singh is a leader. He is a sincere guy an expert in finance. That US system is better that the process they go through to become a President, American chose a leader.
I ma not sure how you would define leadership? Leadership to me is charting the course for the country whether its overt (through speeches or grand displays) or behind the scenes by setting the right policies. Based on this definition Manmohan Singh is a leader.
If you're expecting a tall strapping fellow with a gnarly mustache dominating people, then sure Singh is not your man.
Since you think that the US is so great in selecting leaders, I am assuming you like the heavy handed rhetoric of Bush or the sniveling lies of Clinton.
In terms of Pakistan, Quaid E Azam, Liaquat Ali Khan, Ayub Khan, ZAB, and BB could be considered 'leaders' on the international level. Folks like Zia, Yahya Khan, Jamali, and Nawaz Sharif could hardly had a 'presence.'