why does there not being any actual communist nations (by the very definition) mean to you there is no capitalist nation? we are in one right now.

Capitalism is a historical development from feudalism, so you don't need communism as a point of comparison/contrast for capitalist nation to exist.

Also, the "communist" countries are, strictly speaking, capitalist if you look at their mode of production and mode of distribution. Stuff is made largely for profit, there's private ownership, markets, things are distributed via money. As a wise man once said, name doesn't make a thing.