Based on the information in the excerpt, the best inference regarding the effect the war between France and England had on the United States is:
The attacks on American shipping vessels led to a build-up of an American naval force.
This inference is supported by the statement that American shipping was "almost defenseless against French privateers" initially, but by 1800, "armed merchantmen and U.S. warships were clearing the sea-lanes." This indicates a clear response to the attacks that involved increasing military preparedness at sea.