ha ha, so are you now going to spell criticism, criticizm?         
Adding -er/-est | Adding -ing/-ed | Adding -ly | Adding -s
-ible or -able | -ie- or -ei- | English & American English
English and American English Spelling

Here are the principal differences in spelling between English and American English.
        English         American English

Final -l is always doubled after one vowel in stressed and unstressed syllables in English but usually only in stressed syllables in American English, for example:
        

rebel > rebelled
travel > travelled
        

rebel > rebelled
travel > traveled

Some words end in -tre in English and -ter in American English, for example:
        

centre
theatre
        

center
theater

Some words end in -ogue in English and -og in American English, for example:
        

analogue
catalogue
        

analog
catalog

Some words end in -our in English and -or in American English, for example:
        

colour
labour
        

color
labor

Some verbs end in -ize or -ise in English but only in -ize in American English, for example:
        

realise, realize
harmonise, harmonize
        

realize
harmonize
Common Differences
English         American English
all right         all right, alright (disputed)
analyse         analyze
centre         center
cheque         check
colour         color
counsellor         counselor
criticise, criticize         criticize
defence         defense
doughnut         donut
favour         favor
fibre         fiber
flavour         flavor
fulfil         fulfill
grey         gray
honour         honor
humour         humor
jewellery         jewellery, jewelry
judgement, judgment         judgment
kerb         curb
labour         labor
license, licence (verb)
licence (noun)         license (verb)
license (noun)
litre         liter
metre         meter
mould         mold
neighbour         neighbor
offence         offense
practise (verb)
practice (noun)         practice (verb)
practice (noun)
pretence         pretense
programme (plan, concert etc)
program (computer software)         program
program
pyjamas         pajamas
realise, realize         realize
savour         savor
speciality         specialty
theatre         theater
travelled
travelling         travelled, traveled
travelling, traveling
tyre         tire
valour         valor
why do you americans mess about with our language?