In my opinion, I think one of the reasons why Japan has unique culture in the world is involved with the fact that Japan has never been conquered by any other country so far.
This fact is due to the location where Japan is in the world and some historical accidents that are the closed nation called SAKOKU and the failure to invade Japan by Kublai Khan because of sudden storm and so on.
For that, the culture of Japan has rarely been affected by any other country, and it had grown gradually, and finally it became unique.
In my opinion, I think one of the reasons why Japan has such a unique culture is related to the fact that Japan has never been conquered by any other country.
This is due to the geographical location of Japan and some historical events such as SAKOKU when Japan cut off all ties with the outside world and Kublai Khan's failed attempt to invade Japan.
For these reasons, Japanese culture has received little influence by other countries, and has developed gradually into its unique identity today.
1. ”such a” is correct, not “such an”
2. “so far” in 2nd line in 1st paragraph before collecting, implies that there is a possibility in the future.
cut off ties with ~