I´m sending my cards from Austria since 2019 always as Priority mail and there are sometimes issues with cards travelling to the USA. I´m sending big bunches of more than 100 cards once a month and it happen several times that all cards to the USA (including locations like Hawaii or Guam) are completely lost. I do not know where is the issue but I expect that on the side of USPS, because all other cards from the bunch reach their destinations without any problem. I´m using tariff “Brief International Plus” that cannot be payed by stamps, so all my cards has only postmarks and I guess that this can be the issue for some sorting machines in USA considering the cards as not payed. When I resend the cards to same addresses two or three months later than everything is OK and the standard travelling time from Austria (Poysdorf) to USA is 14 days.