The president of the US is an elected executive official of one country. His power is far from absolute. We have, in the United States, a division of power among the President, the Congress, the Supreme Court, and of course the states.
When you really look at it, the president doesn't have all that much pull. Even within his limited scope of power, he must answer to the electorate. He must answer to special interests.
The pope, on the other hand, has the spiritual devotion of over 1 billion people. He has no donors or special interest groups to answer to. He has no electorate to answer to.
So yes, the pope is more powerful, quite clearly.