A few other points.
The French obviously have a couple thousand years head start on American producers, but that doesn't mean that we haven't learned anything.
A lot of varietals in the US are actually blends. By law, a wine in the US labeled as a varietal must have at least 75% of the specified grape. Many winemakers add fractional amounts of other varietals to round out the flavor. But if you have a particularly spectacular block of cab or Syrah, why not showcase the single grape?
That being said, American wineries do make some world class blends.
The Meritage Association was formed in 1988 by a small group of Sonoma County and Napa Valley, California vintners increasingly frustrated by U.S. Bureau of Alcohol, Tobacco, Firearms, and Explosives regulations stipulating wines contain at least 75% of a specific grape to be labeled as a varietal. As interest grew in creating Bordeaux-style wines, which by their blended nature fail to qualify for varietal status, members sought to create a recognizable name for their blended wines.[1]
https://en.wikipedia.org/wiki/Meritage
There's also a group called the "Rhone Rangers" that specialize in producing Rhone varietals and blends. This is a big thing in some of the Central California AVAs.
https://rhonerangers.org/who-we-are/mission
Tablas Creek produces an awesome array of Rhone wines from cuttings that they originally started importing in the 1980s.
https://tablascreek.com/story
The winery is actually a partnership with Chateaux de Beaucastel, one of the great estates of Chateauneuf-du-Pape. They are probably the only winery in the world (including France) that grows every Rhone varietal. They are most well known for their blends, but they also produce most of the varietals, which can be very interesting to drink individually. Syrah, Mouvedre, Grenache and Tannat can be especially good on their own.
The French are constrained by laws in each particular appellation as to what grapes and types of blend they can produce. In the US, you can mix just about anything as long as you don't call it a varietal. There are some really creative winemakers out there creating some great blends using mixtures of Bordeaux and Rhone grapes, and even adding Italian varietals and Zinfandel.
The winemaker at Tablas Creek has his own winery, Lone Madrone, where he creates some really interesting combos.
https://www.lonemadrone.com/
