Question

What countries currently participate in the summer olympics

Answer 1

Eleven Countries/Nations (Unites states, Switzerland, Austria, Denmark, England, Germany, Australia, France, Greece, Hungary, and Sweden)

Answer 2

There are many countries that participate.

It's a lot to list so if you go to Maps of World 2016 Summer Olympics Participating Countries, you can see all recent countries that participated. This way you can also give credit to that site.