Grammar Differences Between American and British English

WILL OR SHALL

• British English: 

Will or shall can be used with I/we:

E.g. I will/shall be late this evening.

The questions shall I...? and shall we...? are used to ask for advice, etc.

E.g.: Which way shall we go?

• American English:

Shall is unusual

E.g. I will be late this evening.

Should I...? and should we...? are used to ask for advice, etc.

E.g. Which way should we go?

NEED

• British English: 

You can use needn't (do) or don't need to (do):

E.g. We needn't hurry or We don't need to hurry.

• American English:

Needn't is unusual. The usual form is don't need to:

E.g. We don't need to hurry.

DEMAND

• British English:

After demand, insist etc. you can use "should":

E.g. I demanded that he should apologies.

We insisted that something should be done about the problem.

• American English:

The subjunctive is normally used. "Should" is unusual after demand, insist etc.:

E.g. I demanded that he apologize.

We insisted that something be done about the problem.