The U.S. goods and services trade deficit with the EU was $109 billion in 2018. The U.S. goods and services trade deficit with China was $378.6 billion in 2018.
The US certainly has little interest on a strong united EU. But there are a lot more factors at play. Like having military bases there. And generally a lot more soft power / cultural influence. Still, do you remember the US announcing tariffs on car imports?
The US has used groups like NATO and the G7 to ensure that no European power would challenge US hegemony.
The UK has long[1] been seen as the America's cat's paw/poodle in the EU[2] - which is why some in the EU are of the idea that Brexit's silver lining is the end of British obstructionism.