Take guns. For Americans guns are a legally enshrined right whereas in Britain guns have been rejected by society to the extent that even most police officers are not allowed to carry a gun.
I would not want a LLM telling me that guns are useful for self defence because from my cultural perspective they are not and owning a gun for self defence is actually a serious crime.
Likewise I would not expect that perspective to work for many Americans. If you live in the middle of nowhere and there's no police for miles around, then owning a gun for self defence seems like an important right to have. It's just not a right that is applicable to my cultural circumstances.
That's a deliberately mild example, there are of course more serious cultural incompatibilities that are almost impossible to discuss online in the abstract without setting off a debate on the thing itself.