On possibility is that the 're' and 'er' spellings had different denotations, which is what this article implies about the difference between theatre and theater in American English (
http://grammarist.com/spelling/theater-theatre/). A 'theater' referred to the location or venue, but 'theatre' to the art form. Similarly, 'centre' would detonate the middle, while 'center' a location.
The google N-gram for 'theatre art' and 'theater art' seems to support this proposition - 'theatre art' in American English was more widely used until fairly recently, perhaps now the distinction is losing itself to a drive for consistency in spelling. However, I expected the results to be be confirmed by Ngrams for 'theatre critic', or even 'theater seats', but these seem to have been used fairly interchangeably until around the 1970s. Similarly, Ngram for 'centre point'/'center point', and 'dead centre'/'dead center' don't indicate that these two spellings carried different meanings. It seems, then, that the use of two spellings for different meanings is unlikely to be a reason for the delay in the adoption of the American spelling.