Typical European red fox;

Typical North American red fox;

The main differences are in the coat. Euro foxes have short, dense coats with a fairly coarse texture. Their coats are designed for a wet climate and I’ve seen rain literally run off a fox’s coat without getting them wet. North American reds have coats more designed for dealing with cold and snow. Their fur is longer and much finer and softer in texture. I have pelts of both European and a NA fox and the texture is noticeably very different.

Left is a European fox, right two NA foxes. Euro foxes are a little bigger than American ones and the colour tends to be a bit duller/darker with more frosting over the hindquarters. You don’t see many light coloured foxes like the western US one in Europe. Grey coated foxes are also common in Europe but rare/absent from American ones. Colour does vary a lot depending on region though. The cross morph is also does not occur naturally in European reds. 

From what I understand, NA reds have shorter muzzles and ears, bigger, wider feet and their legs tend to be a bit longer than European foxes (although this varies by sub-species.) The black markings on the legs in Euro foxes tends not to extend more than half-way up the leg and is more of a very dark brown, whereas on American foxes the black often extends all the way up the leg. The exception are grey morph foxes which have more prominent black markings. In summer the black markings recede and fade in Euro foxes but often don’t in American reds. American reds also typically have bigger white tips to their tails and it’s common for European foxes to have black-tipped tails.

Like I said it does vary a lot depending on country/region. Eastern US reds are pretty different from Western reds and tend to have more features in common with Euro foxes (possibly due to releases of European foxes in those areas?) In Europe there can also be quite a bit of variation. Even in the UK, foxes from southern England are smaller and lighter in build than those in Scotland.

Also for fun, here’s a suspected European/American red fox hybrid. This fox was found living wild in the UK but clearly has features of both and it’s coat does not seem to be giving it much protection from the rain;