If The United States has proven supplies of natural gas in the ground, but France doesn't, the United States has what kind of advantage in terms of trade?

The United States will now be able to Export Natural Gas to nations that have a demand for Natural Gas, resulting in economic gain. This is opposed to France, who without Natural Gas supplies will now have to rely on importing from the U. S and other Natural Gas exporters.

In short, the U. S can make money off their natural resource, whereas France cannot and instead would have to spend by importing Natural Gas.