different usages in verb tenses

You mean like this?

"British" English:

I've lost my key. Can you help me look for it?
I've already seen that film.

American English:

I lost my key. Can you help me look for it?
I already saw that film.

There are many more differences than that. Many words are spelled differently, there are lots of differences in verbs and their uses.

American and British English are the two varieties that are taught in most ESL/EFL programmes. Most people agree that no one version is "correct".

The most important rule of thumb is to try to be consistent in your usage. Stick to one or the other. Which one is 'best' is a matter of personal opinion. I myself was taught 'British' English, and my own personal opinion is that it is more elegant and intelligent, but I expect other people will disagree.

A factor in your choice might be whether you plan to work or study in an English speaking country, and if so, which tradition that country follows. For example, Canada tends to follow the US pattern, while Great Britain, Ireland, Australia, New Zealand, South Africa etc tend to use British English.

Re: different usages in verb tenses


NaE [AmE & CdE] does not always forsake the present perfect for these types of situations, Muoyuer. There is a very important distinction at play here.

This present perfect is the PP of consequence but not every finished action has a great consequence in a speaker's mind, so we choose the present perfect if we want to add importance to a finished action, "losing one's key" or we use the simple past to give it less importance/greater casualness.

NaE tends to be more casual so you more often hear simple past but the present perfect is there if we feel the need.

This use of the PP has long been a special area of interest for me and I tend to disagree with Contrex. From my experience in a multicultural milieux that included speakers from all dialects, I noticed/have noticed that in casual conversation, all speakers tend to use both the PP of consequence and the present simple in the NaE fashion.

One BrE language authority, I believe it was Michael Swan, mentioned that BrE is moving towards the NaE model for this particular language structure, but I haven't seen any corpus studies done to verify it..