Asko?Eurotech,Malber, LG, Summit, Supra (sp), and others all sell combo units on the United States market. LG is Korean, while most all the others are either rebadged European or IIRC Asian models.
Summit or Supra IIRC offers a 220v combo washer/dryer, all the rest are 120v. Malber offers a 220v dryer, but their combo unit is 120v. My guess is the market for such units is small to begin with, and requiring 220v power would limit the market more. Most people looking at such units are in apartments, and may not be able, for various reasons to install 220v power. Miele,Bosch, AEG, and others make 220v combo units, but doesn't even bother selling them in the US.
Nearly all reviews on both sides of the pond on combo units say the same thing; even the best of them have draw backs, and if one can possibly swing it, install separate washer/dryer units.
For the American market, with it's large homes/loads of laundry, the best design would probably be a full sized unit running on 220v/30amp power that was vented. Even then such unit would require regular upkeep to run properly. Just the thought of all that lint and detergent residue seems like a fire waiting to happen under the right conditions.