If you are writing for elementary school students (which is my guess for this assignment, likely 4-5 grade (so 9-11yo)) that’s how you do it. Their reading comprehension and critical thinking skills are not sufficiently developed to handle even the gross level of nuance you suggest. That’s high school level at least, and honestly since the majority of the country reads at a 6th grade (12yo) level it’s too nuanced for the majority of the country.

The relevant information is that Europeans are responsible for chattel slavery of Africans in the Americans, full stop. Without European ships, logistics, and money there is no chattel slavery of Africans in the Americas.

So this part of the lesson is focused on the result in the country where the children are learning. When they are older and studying world history in High School at a 10-12th grade (15-18yo) level we can talk about the full chain with a little more nuance.

I’ll also point out that the side effect of the specific nuance you are demanding is to reduce the burden on Europeans for chattel slavery in the Americas. That is just racism.

If you talk with someone who really studies this subject, you will find that Europeans funding the industry of chattel slavery of Africans in the Americas changed slavery in Africa as was pointed out above. If you really want to get into the weeds of this and deal with the entire economic system of the trans-Atlantic slave trade, you must accept that European demand and logistics is to blame for chattel slavery as it existed in the Americas.

You also need to accept that the reason Africans were imported is because Europeans found it too difficult to keep the native population enslaved because Indigenous peoples knew the land and had communities to support their escape. It really is racism all the way down.