The X-Men is one of the most multi-national teams in Marvel. Don't expect most of them to follow American trends.
Well there are people from other nationalities,
most are indeed American, or at least the core ones people think about...
Cyclops, Jean, Jubilee,Dazzler,Kitty, Emma, Rogue, Iceman, Angel, Beast, Forge(Cheyenne) , Gambit, Havok,Polaris, Professor X(I know, Patrick Stewart, but sorry guys. X is American.)
Still, you have some that aren't. Storm, Wolverine, Piotr, Magik, Nightcrawler Psylocke, etc, etc, most I'm pretty sure are American and would probably follow American trends to a general degree, though they are usually outcasts, so there is that.
I think Avengers have close to the same amount if not more non Americans.
Doesn't Null learn how to turn off his nullification power eventually with Jean? i was convinced that while normally his nullification works on its own without Null's input he CAN turn it off and allow his mind to be read deeply.
There is that one training session with Rogue where he turns off his nullification and touches Rogue and on pure instinct his power turns itself back on as he realizes how dangerous Rogue's power is, but i was assuming that happened because his power felt IMMINENT DEATH the second he touches Rogue. I don't think he would have quite as strong a reaction if it was just his memories being read by Charles or something and he was willingly turning off his power for it to happen. Tho i guess we haven't seen what happens in a willing and calm situation, the example i gave was more of an instinctual fear reaction.
Which is why Boots said
Null's power only blocks malicious or invasive attempts at mind reading. It's why Jean and Xavier are only able to see surface thoughts.
If somebody wants to talk telepathically with Null, and Null doesn't perceive it as a problem his body allows it. If somebody wanted to read his memories it might be an auto block if Null isn't aware or prepared for it, but if he consciously allows it, I'm sure he could allow Jean or X to read him.