"Why do people insist on calling it the American Church, the French Church, etc."
Its a little more than semantics. Amchurch has its USCCB, which voted overwhelmingly to leave it up to the individual bishops to violate canon law and give Holy Communion to public facilitators of abortion, to turn Ascension Thursday into Ascension Sunday, etc.
Canada has its own CCCB, which makes its own rules, etc.
Prior to VC II, Catholic meant universal. New Church, however, defines Catholic as diversified.
Heck, nowadays you can even be catholic while remaining outside the Catholic Church.
I loved how when after the new watered down canon law (1983) came out that had already gutted our fasting practices, the USCCB was instructed that they could forget about fasting on Fridays altogether, just have some form of unspecified penance in its place.
Not only was the watered down fasting watered down even further - to the point of nonexistence - but our illustrious leaders forgot the part about adding any penance. So now American Catholics aren't required to fast, or do anything whatsoever for that matter. An integral part of our community and reverential sacrifice to our Lord flushed down the toilet by so few in so short a time span.
Another blessing to our Church from John Paul "the Great" and the American episcopate.