I eat my words. Had a closer look at the broadside using a magnifying glass and it could say 'Bible and Heart, Church St. Salem.' If that is right I'd say it's the earliest American broadside I've ever seen even if it is 1720s. I suppose if a London printer went across towards the end of the 17thc taking his stock, type and press with him, it's quite possible he was printing still in the 1720s using older materials and style. I'll try to investigate further but if it is American you're probably better placed anyway.