Lord! Every wine in France is grown on American root stock which replaced French Phylloxera infested stock. The plant are very similar.
After WWII, many French vineyards were also replanted with California root stock.
Umm, not sure here, but I think that's another term for "Cheeze eating surrender monkey infestation". Surrender monkeys can screw up a decent wine, for sure!
Seriously, some moderately priced California Cabernet Sauvignon or Merlot wines compare very well with much higher priced Bordeau and Beaujolais wines from France. Hmmm, should I buy the excellent Meridian Cabernet for $12.00, or should I spring for the B&G Beaujolais for $25.00? Actually, price neutral, I prefer the California wines!