How many people use Gmail in a language other than US English? How many people change their UI language and rename folders such that there is a clash?
Optimise for where it will have the most impact, and develop a work-around for the minority of users where this causes a problem.
You'd be surprised. There are only about 400 million native English speakers [0], and Gmail has 1.5 billion users [1].
If we assumed that all native English speakers use Gmail, they'd represent not even a third of the users. Of course, there are many non-native English speakers, but I'd assume a significant fraction of them would prefer to use Gmail in their language.
I'd argue i18n has a huge impact, but Google really doesn't optimize for it.
[0]: https://en.wikipedia.org/wiki/English_language [1]: https://www.cnbc.com/2019/10/26/gmail-dominates-consumer-ema...
I, personally, have 3 "GMail" accounts: one @gmail.com, one @ my own domain, and one for work. So if I were the average English-speaking user of GMail, having every English speaker be a user would pretty much cover the 1.5 billion.
(I do not, in any way, think I am the average—I merely seek to point out that it's significantly more complicated to calculate than your post suggests.)
Don't assume that only native English speakers (want to) use things in English.