British and English Differences

Differences in American and British English grammar - article
Introduction
Speakers of American English generally use the present perfect tense (have/has + past participle) far less than speakers of British English. In spoken American English it is very common to use the simple past tense as an alternative in situations where the present perfect would usually have been used in British English. The two situations where this is especially likely are:
(i) In sentences which talk about an action in the past that has an effect in the present:
American English / British English 
Jenny feels ill. She ate too much. 
Jenny feels ill. She`s eaten too much. 
I can`t find my keys. Did you see them anywhere?
I can`t find my keys. Have you seen them anywhere?
(ii) In sentences which contain the words already, just or yet:
American English / British English 
A: Are they going to the show tonight?
B: No. They already saw it.
A: Are they going to the show tonight?
B: No. They`ve already seen it.
A: Is Samantha here?
B: No, she just left.
A: Is Samantha here?
B: No, she`s just left.
A: Can I borrow your book?
B: No, I didn`t read it yet.
A: Can I borrow your book?
B: No, I haven`t read it yet. 
1. Verb agreement with collective nouns
In British English collective nouns, (i.e. nouns referring to particular groups of people or things), (e.g. staff , government, class, team) can be followed by a singular or plural verb depending on whether the group is thought of as one idea, or as many individuals, e.g.:
My team is winning.
The other team are all sitting down.
In American English collective nouns are always followed by a singular verb, so an American would usually say:
Which team is losing?
whereas in British English both plural and singular forms of the verb are possible, as in:
Which team is/are losing?
2. Use of delexical verbs have and take
In British English, the verb have frequently functions as what is technically referred to as a delexical verb, i.e. it is used in contexts where it has very little meaning in itself but occurs with an object noun which describes an action, e.g.:
I`d like to have a bath.
Have is frequently used in this way with nouns referring to common activities such as washing or resting, e.g.:
She`s having a little nap.
I`ll just have a quick shower before we go out. In American English, the verb take, rather than have, is used in these contexts, e.g.:
Joe`s taking a shower.
I`d like to take a bath.
Let`s take a short vacation.
Why don`t you take a rest now?
3. Use of auxiliaries and modals
In British English, the auxiliary do is often used as a substitute for a verb when replying to a question, e.g.:
A: Are you coming with us?
B: I might do.
In American English, do is not used in this way, e.g.:
A: Are you coming with us?
B: I might.
In British English needn`t is often used instead of don`t need to, e.g.:
They needn`t come to school today.
They don`t need to come to school today.
In American English needn`t is very unusual and the usual form is don`t need to, i.e.:
They don`t need to come to school today.
In British English, shall is sometimes used as an alternative to will to talk about the future, e.g.:
I shall/will be there later.
In American English, shall is unusual and will is normally used.
In British English shall I / we is often used to ask for advice or an opinion, e.g.:
Shall we ask him to come with us?
In American English should is often used instead of shall, i.e.:
Should we ask him to come with us?
4. Use of prepositions
In British English, at is used with many time expressions, e.g.:
at Christmas/five `o` clock
at the weekend
In American English, on is always used when talking about the weekend, not at, e.g.:
Will they still be there on the weekend?
She`ll be coming home on weekends. 
In British English, at is often used when talking about universities or other institutions, e.g.:
She studied chemistry at university.
In American English, in is often used, e.g.:
She studied French in high school.
In British English, to and from are used with the adjective different, e