French flour (farine) is a "Type 55" flour that is most commonly used in France for baguettes and even many pastries (it's close to American all-purpose). Most avid American bakers desire to replicate this flour but it is an extremely hard to do. There are several important differences between American and French flour that make a direct equivalent almost impossible.
One of the main differences is French flour is milled and mixed to a different standard compared to American flour. Typical French bread flours are what are know as "straight" flours. A straight flour is what you get when you grind a wheat berry, remove most of the bran and germ and a) don't sift it into lots of different grades and b) don't mix it together with other grades from other batches (as American millers usually do). The result is a flour that is coarser than a normal American bread or all-purpose flour.
The character of the protein (gluten is also quite different in a French Flour, not nearly as elastic as the kind you find in American flour. Though French Type 55 flours routinely list a protein content of around 11.5 percent, they perform more like a medium-protein American flour, around 9.5 percent. That puts them in the American all-purpose flour range.
Plenty of bakers try to replicate baguettes or other French breads with high-gluten flours (or mixtures of low and high gluten flours) but the experts are mostly in agreement that to much American gluten is bad for a good French bread. Bottom line, there is not much about American and French flours that are the same except the fact that they are all flours. They are different types of wheat grown in different places, under different conditions, then processed differently and milled differently. The end result is that they behave differently even when used in the same types of application.
This does not mean it is hopeless to try and make a good baguette out of American flour. It means, simply select a good, hard all-purpose flour (preferably a Northern one made from a hard red winter wheat) and you are at as good a starting point as any baker on this side of the pond.