My intuition is that German, for example, is much less active of a language in the US, where immigration peaked long ago, than Chinese, where immigration is active.

The first two are presumably recent immigration.

Kentucky in particular surprises me despite my German ancestors settling in Indiana during the 19th Century. I had assumed Kentucky had been English immigrants from colonial Virginia/Carolina.

This is enough to discredit the whole infographic in my eyes. No matter what the CPC or anybody else may claim, these are distinct languages, and not dialects. Not only that, but in some of these places a lot of Chinese speak other regional Chinese languages, such as Fuzhounese, rather than Mandarin or Cantonese. (I remember a blog from twenty or so years ago by a NYC Chinatown native who mapped his building by language; something like a dozen Chinese languages were spoken by residents of that building's apartments.)