You are correct in thinking that British and American English is different. One difference I've noticed is in motorcycle magazines: Americans tend to say "Yamaha is" whereas British magazines say "Yamaha are."
I'm not sure if that is due to someone not catching a mistake, but it seems to be that way in more than one magazine.
I don't believe there's any dialectal difference in the use of at/on. What oldspice is referring to is probably the treatment of collective nouns, in which there does seem to be a difference. For nouns that describe a group/collection of things or people (such as 'family') UK usage dictates they could be plural or singular ('the family is/are in the house'), whereas in the US they are usually treated as singular (i.e. 'the family is in the house').
Does anyone help me what is deffrene between " at / on " i confuse about that, why i heard from some people that "at/on " the same meaning becuase the says (at ) is american on(on) is british is it right or wrong
One difference which I have noticed is with regard to "weekend".
American = I always watch several movies on weekends.
British = I always watch several movies at weekends.