They are called potlucks or cookouts in the U.S. and they happen all the time.

In fact, they are probably a lot more common than having a huge party (so large that you have to invite people in batches of half a dozen at a time) completely planned and executed by a single person.

This article is good, don’t get me wrong, but this type of event planning is not really representative of how folk in the U.S. get together

Some summers I plan on BBQing every weekend and I throw invites out on Thursday. People typically bring something and we all have a good time.

For the parties as described in the article, I maybe go to one or two a year tops. Before I had a kid I used to host large parties like the kind described (~15 people tops though), now I just attend and contribute.

I live in the US, and the type of party in the article is way more familiar to me than potlucks or cookouts – but that's just me

Yes but it probably has a bigger overlap with the kind of people that would use Google to find an article that says how to throw a good party.