The advantage UK self-pubs have is with only a little basic Americanizing, they can to tap into much of that huge US market. Some online outlets are pose a challenge as they need a US bank account to receive payments, but that's not entirely impossible to solve.

Where UK self-pubs are more likely to come unstuck, I think, is in publishing to non English speaking countries as the translations costs are going to be prohibitively high in most cases.