How far back do you want to go? France had a very good understanding with Germany in WW2 after its surrender. France worked well with and helped Germany under occupation. The US also had Operation Paperclip and other technical needs that where filled by Germans after WW2.
The US was also aware of some early French atomic power work and patents from the 1940's that would have made total US control of post war nuclear power interesting. The US was not going to allow France get into the lucrative post war nuclear age with early French nuclear patents.
The US interest in French codes goes back to the TICOM
https://en.wikipedia.org/wiki/... efforts at the end of ww2 to see what France (and free French during ww2) was going to do after ww2. The US and UK found a unit of Italian code experts that had an understanding of French methods in the 1940's and used them (under TICOM) to break French diplomatic traffic after ww2.
As France was rebuilding this flow of embassy traffic was vital to the US and UK as they got product from French embassies in eastern Europe.
At some point France finally worked out it was losing all its embassy traffic to the US and UK and finally worked out how to shield some of its crypto hardware (total tempest leaking is not good).
Into the 1950's the US put massive efforts into French product. By the early 1970's France was working well with the UK (at a JIC level) and US in all military and crypto areas.
France worked well with the UK over the Falklands, offering all technical details to the UK on systems delivered. The 1987 Libya and Chad boarder war saw the French, CIA and UK work very well together.
The US fear is that quality French brands and products will sell well at a good price and be in demand around the world. South America, Africa, Asia. All parts of the world the US expects to push new US products and services into.
So France and its top exporters are under constant surveillance by the US gov until the US can capture all French export markets.