Difference between English and English International for Windows 10 .ISO?

Esentially, they are the same. The International version contains localized English keyboard languages (like United kingdom, Australia, etc.).

While the en-US (English) only contains the minimum of English-based languages.

UK one has colour instead of color and favourites in place of favorites, that's it really.... Keyboards, time and date, measures systems these are THE same in both and in separate setting of region NOT language (when you install windows you can choose any region on any language version) My recommendation is stick to US version since UK one needs separate upgrades and it's problematic later on...