"In Japan, people like to eat sushi."
And on the surface, there's nothing wrong with the grammar, so it seems OK. However, it's probably not what the speaker means. There are two important points.
First, when you have a choice between a noun and an adjective, it's considered better English style to use the adjective, so "Japanese people like to eat sushi," is better.
日本語では、名詞に助詞を付けるので、英語より名詞を使う。だけど、英語では、助詞がないので、名詞より形容詞をよく使う。Pardon my Japanese grammar mistakes, if there are any.
Second, we do not often say "In Japan, ~" at the start of a sentence.
Think about what you are saying when you say: "日本では、~ やる." You are implying: "他の国では、~ やらない." You might not mean that every time, but it's certainly implied.
内・外 is a very common cultural concept in Japan and some other countries, but to my knowledge it's NOT an important cultural concept in any English-speaking culture.
For example, if you go to the USA for an MBA program, you will not be called an "alien" or "foreigner," both of which imply 内・外. Instead, you will be called an "International student."
Here are two important American cultural concepts which oppose the 内・外 distinction:
- The melting pot is an older idea (Wikipedia has this one in Japanese)
- The salad bowl is more recent (This one is just in English)
The point is that in a pot or in a bowl everyone is 内 and there is no 外. So if your grammar implies an 内・外, you might confuse your reader or listener.
Please use English well!