I’ve moved your post here, since other postcrossers were discussing this same issue earlier this year.
You have the option of several postcards travelling to the same country at the same time ticked in your profile.
That means you will get the members waiting at the top of the address pool irrespective of country.
When you joined Postcrossing that was unticked (default) so you have ticked the option since joining.
Currently we have many active Russian, German and USA members and they are the ones waiting at the top of the pool.
Select Settings (found under your profile picture) and then select Profile. Untick Same countries in your profile (found at Postcrossing options) and don’t forget to save the change with the button at the bottom of the Settings/Profile page.