If everyone is your friend then no-one is. I wouldn't say curt and standoffish, but it's good to keep a certain amount of distance and formality with people you're not actually friends with so that you both know where you stand.

Unless friendliness is an expected social signal, and there's a separate signal, known to the local culture, but not to you, that says, "I'm being nice but we aren't actually friends".

Well I said outwardly friendly. As in like we grew up together in the same neighborhood kind of friendly.

Same happened when I had interviews for American companies. They were so excited about everything and overly enthusiastic I can't help but thing I'm being interviewed by psychos.

In the United States this is considered a "normal" amount of politeness. In some other cultures it is considered weird and fake. Some Americans go abroad and complain everyone was "rude" to them not realizing the cultural differences.