A generalization is a general statement or concept obtained by inference from specific cases. Mostly your specific cases. Fun fact: In the American and Canadian English many words use z instead of s which differentiates them from the common and native British spellings of the world. In the UK it's usually generalise.
Generalizing is great, because It allows us to make shortcuts in conversations, but you need to be careful when generalizing in English. You need to accept that not every foreigner you talk to behaves or thinks in the same way as you. Japan is a high-context culture and the Japanese people in Japan are very relational, collectivist and contemplative. As you know, I'm from the U.S. and it's a fusion of nationalities, cultures and ethnicities. We have a low-context culture so individuals communicating will have fewer relational cues when interpreting messages. It is necessary for more explicit information to be included in the message so it is not misinterpreted.
Also, why would you go to an English Conversation school and make shortcuts in conversation? Let's talk!
I love food! All food from every country! I want to try it all....but I dread talking about it in class most of the time. Dread it! I dread it because of the generalizations. "Korean food is too spicy!", "Chinese food is dangerous!", "American food is too sweet!" Food is an important part of culture and culture is a strong part of people's lives. It influences our views, our values, our humor, our hopes, our loyalties, and our worries and our fears. So when you are communicating with people and building relationships with them, it helps to have some perspective and understanding of their cultures.
It's impossible to have a conversation with someone who has already decided on what they want to think about something and are not interested in anything that doesn't support their thoughts. Don't be this person!