A winemaker in the USA can add any of these sweeteners to their wine without disclosing the info to the consumer.

Maltodextrin
Sucrose
Glycerol
Sorbitol
Dextrose
Fructose
Glucose
Invert sugar
Artificial sweeteners

The only way to know what is in your wine is to ask the winemaker directly.
Shake your Winemaker's Hand