There is an American bank which will lend to US, UK and Canadians.
70% loan to value.
Minimum of $100,000 mortgage (I have also been quoted $150,000)

So minimum valuation of about $143,000 (or $215,000 if the second quote is correct).

The biggest problem I can see is if the purchase price has been inflated above the valuation and you were unable to qualify because the mortgage was therefore lower than $100,000.

Dont know how the current credit crunch will have affected product availability either - generally cases have to be very "clean" for expatriate mortgages in other countries - most likely the same for this product.