US for sure. Since it only pulls from TransUnion, it probably won't affect your credit at all. (And it's 40K unless you do a BT).
For many people BofA pulls EquiFax instead of Experian so they may be a freeby too. Their two Hawaiians for 35K each are hot now. (One's technically BofH but still FIA corp). I also like their Virgin Atlantic as you get 50K usable on US and other partners and you earn 1.5 miles for every dollar spent and 1100 miles for every Hertz or Avis rental.