English Cream Golden Retrievers

The shortest explanation to this is 2 things.

1. Coloring - European standards for the golden retriever allow for any shade of gold or cream (white), but exclude shades of red and mahogany.   American standards allow for any shade of gold, light or dark, but exclude the extremes on each end (white and red). 
2. Body Frame - English Goldens tend to be a bit shorter, longer and more muscular.  American Goldens are a tad taller and some of them (particularly goldens breed for the field) are leaner.

There are some out there that may make a case to say that health is another difference.  Particularly rates of cancer (slightly lower in English Goldens) and commonly inherited genetic dieases.  It is my opinion that this may have some weight only to the extent that the American Golden Retriever has been "over bred" to try and conform to a particular standard set forth by the AKC.  Specifically, excluding certain colors and/or body frames, thus reducing the genetic pool.   Allowing for more variance in genetic traits expands the gene pool and thus reduces "over breeding".  

Ultimately, what combats the common health problems associated with any breed is responsible breeding practices.  This includes having genetic testing done to ensure that pups will not inherit any of several genetic dieases common to any golden retriever.  Additionally, having heart certifications and eye certifications done.   As well as having hips and elbows examined and certified by the Orthopedic Foundation for Animals.   Honestly, if humans started getting on board with this type of testing we could probably reduce many common health problems  as well.