Flaco

I'm no expert on this but it is my understanding that international english is used more as a spoken language and minor variations in spelling such as you mentioned are easy to figure out. Slang words and local dialets are to be avoided as these can be very confusing. As in any language the point is to be understood when speaking and understand when listening.
When writing use the spelling of the country you are from so if there is any confusion in the word usage it is easier to find it's meaning.
There is and always will be a difference between American and English. Like the guy said, "I'am bilingual, I speak American and English". Just be glad you don't have to translate Scottish english! And Scotty on Star Trek doesn't count.