Spelling it center provides the significant benefit of removing foreign orthography from English, making it easier to learn to read and write.

I see no value spelling it centre. That some other languages spell the word doesn't matter as they're pronouncing it without a vowel between the t and r which is rather different than English.

In French it's pronounced santr. In Italian it's sen-tro. In Czech it's tsen-troom. In Swedish it's sen-trum.

Languages that, like English, pronounce it with a vowel between the t and r? They spell it that way.

In Albanian it's qendër pronounced very close to rhotic English sen-ter.

In Norweigian it's senter (sen-ta) which is pretty close to non-rhotic English.

In Croation, it's centar (sen-tar).

In Lombard it's center.

In Swedish, the other word for center (meaning a center (place) or sports position) is spelled... center.

And even Czech, which spells it centrum, changes the spelling to center in the genitive plural, to match the pronunciation.

So even if we're going to choose spelling based on other languages, there's plenty that spell it similarly to center to argue for it in English - though I would still argue that other people are doing it isn't a compelling argument.