Hi. Good question! I am currently a PhD student in the United States. My father is from England, and my mother is from Korea. I've lived in the UK and the US for my entire life, so I feel qualified to answer your question.
"Yosemite National Park had a campfire event."
Your question is whether or not this sentence is grammatically correct.
The simple answer: Yes. You simply have to add a "The," an article, before the sentence to make it flow smoothly. "The Yosemite National Park had a campfire event." Note that I capitalised the N and P of National Park because the Yosemite National Park a proper noun.
But then again, you're asking about one specific portion of the sentence, "had." So let me give you the longer answer to your question.
The longer answer: Yes, but it sounds weird. Just like your native English teacher at your Korean school told you. First, I will tell you why it is grammatically correct and then I will elaborate on why it sound weird.
It is grammatically correct because it is completely possible for Yosemite National Park to have had a campfire event sometime in past.
However, it sounds weird because most native English speakers would then say a specific time in which this campfire event happened. For example: "Yosemite National Park had a campfire event in 2007." This sentence would mean that the YNP held some sort of a campfire event way back in 2007.
Another thing you have to consider, in order to get rid of the "weirdness" of this sentence is whether or not the sentence tells the whole story. Let's assume that the YNP did have campfire events in the past. But do you know whether or not the YNP still has this campfire event? If it still has the campfire event, then the sentence should be: "The Yosemite National Park has campfire events."
And then there's the matter of word choice. As a native English speaker, I would not use the word "had" in that sentence at all. There are much better words that can substitute for it, such as "held" or "hosted" (assuming that you are talking in past tense). Try reading these sentences out loud: "The Yosemite National Park held a campfire event." "The Yosemite National Park hosted a campfire event." See? It just sounds so much nicer. Except I have a feeling that this was a multiple choice question on an exam. In that case, I have nothing more to say.
I want to applaud you for your curiosity. Not many students these days are this eager in their attitudes towards learning. I raise my glass to you.
I hope I helped.