There’s a gulf between English and American spellings AND some American words simply don’t exist in English so you will only find them in American dictionaries like Merriam-Webster where you will find Aluminum - an imaginary metallic substance 
but not Nucular - a popular Americanism for Nuclear
“When I use a word,” Humpty Dumpty said, in rather a scornful tone, “it means just what I choose it to mean—neither more nor less.” “The question is,” said Alice, “whether you can make words mean so many different things.” “The question is,” said Humpty Dumpty, “which is to be master—that’s all.”