I'm thorougly looking forward to Obama's speech in Germany (Geh Deutschland!). But apparently, it's not cool that Obama has so much appeal abroad, because we have to have a president that everyone else in the world hates. This is a great way to pick our presidents (see: George Bush)! It has obviously totally worked out so well for us.
International public opinion does matter. Heads of state all over the world have lost power in large part BECAUSE of their alliances with President Bush. Case in point: Australia, Great Britain, Spain, and Prime Minister Manmohan Singh in India barely squeaked by a vote of confidence a couple of days ago, being accused of being too close to the United States. Currently, in order to hold on to power, the popular thing to do is to take the position completely opposite to President Bush. Domestic pressure necessitates this.
Imagine having a president that people everywhere actually like. What would that mean for us? Heads of state could actually take positions that are in America's interest without having to incurr such massive political costs.
I, personally, would like to have a president that not everyone completely hated.