K9AN (6505km) was the first USA station, and so far the only one, to spot my 10m 500mW WSPR this afternoon at 1418z.
UPDATE 1540z: Still just K9AN spotting me on 10m in the USA this afternoon.
UPDATE 1715z: In the end I got spots from 4 different USA stations on 10m WSPR. I have now gone QRT on 6m (where G8VDQ at 93km was spotted a few times) and on 10m WSPR and am back on 630m (472kHz) WSPR for the evening and night (5mW ERP TX 20%, 80% RX no preamp). So far, on 630m G7NKS (46km) has been copied at -11dB S/N. Still using the earth-electrode "antenna". G7NKS copied me at -22dB S/N. Also copied on 630m WSPR was DK7FC (669km) at -25dB S/N.