for the benefit of those bro or sis, if there are any, i cannot content myself but to access the Google Play store just now. just to be a mythbuster, well, sort of. i have a AMEX with SG billing address and as you guys can witness in the screenies below, Google Wallet indicates it as 'unsupported payment method'. which is not surprising to me but just want to confirm it once again. in case you are wondering, the card that i use is AMEX Platinum and i have been with them for more than 10 years. so it couldn't be new card issue or anything of sort (sh*t, think i watch too many episode of Mythbusters).
on the second screenshot, you can see while trying to add a card, it shows Billing Address with US under it, indicating that Billing Address has to be US. really, it is a no-brainer and the same goes for the states where there is no option for anything other than their 52 states.
i hope this information helps, especially with the screenshots to prove
i heard someone mentioning about Paypal and Debit card... i would love to try those too. damn, i am just so curious about the many claims and if there are loopholes or whatsoever, it will only make me one happy online shopper