No, there is no US- based credit card. But you can always have a international-issued credit card and spend it in the States.

About the expired miles, it really depends on how many miles are going to expire in June. Also, you have to spend all your miles by the expiry date. Unlike AA or UA, just by having an activity once in three years will not extend the expiry date of the miles. So just flying AA in June or making small purchases will not help with your expiring miles. You have to spend them all. There are many ways to spend Asia Miles, you can go to www.asiamiles.com and check what to spend. You can redeem an iPod or restaurant meal or first class tickets or whatever. But the bottom line is that make sure you spend all your expired miles by the deadline. Dont' let it go to waste.

There is another way you can "keep" your Asia miles from expiring. You can renew your Asia Miles for another 3 years. But it's pretty expensive and not very cost-effective.