Depends on what you mean by "US chocolate". There is really good American made chocolate available, although at a pretty high price point. But if you mean regular Hershey, then yeah. But I feel US-made chocolate from Mars or Nestle is better than from Hershey.
But I prefer the quality of other US-made chocolate at a basic price point. I hesitate to say "mass-produced" since most "premium" chocolate is mass-produced.
And this discussion may not be an apples to apples comparison. I know of some people who prefer UK imports and will even pay a steep price for them. Also - I read that these Malteasers I tried are probably made in a factory in Canada, although I'm guessing the chocolate was sourced from the US.