Solar panels are mildly more efficient when colder, the same latitude in an area with similar cloud cover in north America is probably generally slightly better for solar than Europe because it is colder, not sure if it would ever be more than a rounding error though.
The difference between surface solar radiation levels in the US and Europe are wild[1], fully agree on the rounding error view. Anchorage seems to receive the same level of watts per area as Germany and Poland.
