I studied Linguistics at University and every professor I had would call you wrong here. What even is 'proper English?' If you looked at the language as it is in Beowulf you'd see more dissimilarity to our modern English than if you looked at Dutch.
British-English, American-English, Australian-English, Caribbean-English, Indian-English; they're analogous to dialects but on an extreme scale. No one owns a language. In many ways, American-English is closer to what English was at the time of colonial settlement than British-English is today, since it originated prior to the mass standardisation of language with the arrival of the printing press.