Although American English, British English, Australian English, and other English dialects are all very similar, there are still significant differences in the words used by each to indicate certain things.
For example, for just two English dialects:
World Cup sport = football
person who dispenses drugs = chemist
front metal flap of car = bonnet
back metal compartment of car = boot
dot used at the end of a sentence = full stop
straps that hold your trousers up = braces
someone to represent you in a court of law = barrister
World Cup sport = soccer
person who dispenses drugs = pharmacist
front metal flap of car = hood
back metal compartment of car = trunk
dot used at the end of a sentence = period
straps that hold your trousers up = suspenders
someone to represent you in a court of law = attorney
There are literally hundreds of words which have different meanings in different English speaking countries. There are even differences in different parts of the same country. But don't panic. If you know any dialect of English, you can pretty much go to any other English speaking country and communicate easily. But you might have a laugh if you say a word that means something quite different in that country.
>> Can't we say that a football or soccer player is a footballer??
On italki, yes, if you say "football" or "footballer", most English speakers will understand what you mean, regardless of which country they are from. Especially now while the World Cup is going on. It just sounds a little odd for some of us who are accustomed to saying "soccer" or "soccer player".