I'm so confused: Is what is an essay different in every country?

I'm an international student from Japan, and I'm genuinely struggling with the cultural differences in essay writing. Back home, the essays I wrote were much more... indirect. We were taught to hint at arguments, to leave space for the reader to draw their own conclusions. It was about subtlety and suggestion. Then I come to the US, and my professor tells me my essay is 'too vague' and I need to 'state my thesis clearly in the first paragraph.' She said American readers want to know exactly what you're arguing from the beginning. This blew my mind.

You're supposed to just... tell them your conclusion immediately? Doesn't that ruin the suspense? I'm also confused about voice. In Japan, academic writing is very formal and impersonal. Here, my professor wants me to use 'I' and have a 'personal perspective.' It feels so strange. Is there a universal definition of an essay, or does it change depending on where you are? How do I switch between these different cultural expectations?

The cultural differences are HUGE.

In many Asian academic traditions:

• Thesis at the end
• Indirect argumentation
• Reader is expected to infer
• Impersonal, formal voice

In U.S. academic writing:

• Thesis in introduction (often the last sentence of first paragraph)
• Direct argumentation
• Reader needs explicit guidance
• Personal perspective encouraged (especially in humanities)

It's not that one is right and one is wrong—they're just different conventions. Think of it like switching between formal and casual speech depending on context. You're not losing your voice; you're adapting to the audience.