It is true that Germany and France has only been spending about 1.2% to 1.8% of their GDP on defense. US was about 3.5%.
But there are several caveats. First, US's military spending is all over the world, including a large chunk in Asia. Meanwhile, NATO is mostly about Europe. Germany and France cared first and foremost about Europe, and wouldn't be spending money in Asia. So it is not necessarily fair to expect they'll spend equal percentage in military spending.
The other thing is with power comes responsibility. A QB gets all the glory when a team wins because he'll gets all the blame when a team loses. A QB is the highest paid guy on the team, but it is also the most cutthroat position in all of football. Imagine a QB b!tching about him taking the most responsibility. He'll lose the respect of his teammates immediately. US did spend the most, and they also get the biggest say. Every other country has to follow US's lead, not the other way round. That's where the extra money spent in defense gets us.
Lastly, it isn't like US is spending the money on defense because of NATO. It is really to protect our other interests. So it isn't quite accurate to say other NATO countries are freeloader. They just don't have as many interests to protect. This world is a much different place than 1949 when NATO was created. For most of the countries in the world, the need for military has greatly reduced since then.