I also use a NZ Debit card (if this makes any difference, it just a normal visa debit card).
Also, use a VPN, as I know many check the IP address. Cheapest way to get a VPN (that is trustworthy) is to hire a VPS for a year, i.e. this one: https://portal.catalysthost.com/cart.php?a=confproduct&i=0 (check out lowendbox.com for more deals like this from other providers), 1TB Bandwidth a month for 1.42 USD a month. Install openvpn onto the VPS and your computer at home, and you have a fully functional US VPN full speed.
Never log onto the newegg (or other US online computer shop) when using your NZ ip.
Thats all I can think of anyway...