Money in your hand vs money over the counter

After spending years abroad coming home to the United States I was in for some culture readjustments. In the Middle East and in many places in North Africa it is very common when shopping for the cashier to put your change on the counter when giving you your money. The reason being is for the cross-gender mixing in which it’s considered disrespectful to touch the hands of the opposite sex if they are not from your family. So it is very common in all exchanges for people not to give hand to hand exchanges but to do exchanges with money given on the counter. When coming back to the United States I was so used to putting money down on the counter. I was at a store buying some things and the cashier told me my total. I then put $20 down on the counter. The cashier looked at me with a facial expression saying "I know you didn't just put money down on the counter". When I saw her face I remembered, "I'm not in the Middle East anymore". I then apologized and asked the cashier to forgive me. I explained how I just got back from overseas and was used to doing certain things differently and now readjusting. She was interested to know where I been and was very keen to learn about the differences in how people handle money around the world.