That’s because you didn’t see the Brazilian Wines. Visit the Southern Region, in Rio Grande do Sul. There are many wineries of importance, and the grapes and the wine are fantastic. Jolimont, Aurora, and Vale dos Vinhedos, are the best wineries in the South America!
Well, look at it this way: most American wine is made from French varietals (Chardonnay, Cabernet Sauvignon, Pinot noir...), and almost all French vines in France are grafted on American rootstock (because they are resistant to phylloxera, which almost eradicated French vines in the 19th century). So, maybe we're not so different, after all!
Also, at least metric tons are somewhat consistent. I'm guessing in the imperial system, wine would be measured by the volume of some king's bladder or by the amount it takes to fill some long-gone chamber pot in some unheard of castle.
Chauvinism aside, it's pretty difficult for French people, such as myself, to accurately judge American wines, or indeed most foreign wines. I'm sure there are excellent wines everywhere - I have some experience from my travels with Italian, Greek, German, and South African wines, and they all produce some top-quality stuff, so there's no reason why American wines should be different. However, we just produce so much good wine in France, that, whatever type of wine you want, it's usually a lot cheaper to get French wine for the same quality - or, you could get a much better quality for the same price. In consequence, foreign wines are not that easy to find and sample, and there's often not really a point in it. The consequence is that, while the French are often (quite rightly) proud of the quality of their own wine production, many are ignorant about other wines regions.
https://en.wikipedia.org/wiki/Judgment_of_Paris_%28wine%29
Nevertheless, I also prefer French wine.