It is a significant part of your culture and heritage, you should actually read it at least once. It does not need to be the archaic original version, many if not all have meticulously modernized revisions that retain all of the meaning while making it easier to read for modern audiences.
For most countries you would first have to determine what their national epic even is. That is not really a settled thing in a lot, probably even most, countries. But it would be an interesting discussion to have.
Definitely an interesting discussion. And probably even more fruitful to try and go through the most prominent candidates and reasons why they could be the official one, than just half-heartedly going through the one you have been told to be the big one.
Even if your country has a designated national epic, you should see if there are other ones that could have been and what they tell about the values of your culture.
For extra credit, read any comprehensive critical break down of that national epic as well. Few things are as instructive as seeing national myths for the myths that they are.
American: [Visible confusion]
It would have to be The Song of Hiawatha by Longfellow, even if he is currently so far out of fashion as to be essentially forgotten.
I’m pretty sure it would be George Washington parting the Delaware to get to the Promised Land, catching the Nazis by surprise.