Hi Donna. Welcome to Postcrossing, and to the Forum.
You’ll get more cards from the countries with the higher number of active members, which includes the USA, Germany, the Netherlands, China, Russia, etc. Here’s a link where you can look at stats and numbers on the Postcrossing website if you’re interested in a deep dive into those types of details.
I think the following forum topic about discussing the algorithm and how it seems to choose, if it’s fair, etc, is interesting as well:
I have the send to repeated countries option turned on, so I send a lot of cards to Germany, Taiwan, and China, but mostly Germany. I made this change during the pandemic to help balance out the system.
I am not using the option to send to my own country (USA), as I have plenty of friends and family that I exchange mail with here already, and the international exchange is one of the things I enjoy about Postcrossing too.
So yes, you may get a lot of cards from the most active countries, but the longer you participate, the more it may even out over time.