Just had a look at the history of "French Fries". As usual, I got it totally wrong.
It seems that , while the French were experts at deep-frying things, it was the Belgians who established " Pommes de terre frites" (fried potatoes). When the US army was in Belgium (1st World War? 2nd World War?) they took a shine to Belgian "Pommes Frites" and, since the Belgians also spoke French, they became known as "French Fries".
Another story is that Thomas Jefferson, who was Ambassador to France at the end of the 18th century, was a foodie and collected recipes, which he then entrusted his personal cook to prepare. French Fries were sold on the Pont Neuf in Paris during the 1780s. Jefferson brought the idea back to the US, but the "fries" didn´t really catch on until the early 20th century.