This is based on my own limited experience taking apart stomp boxes for repair or setup of trimmers on a scope, designing my own, and modding existing ones for my own use. I've done this plenty over the years but only with a few stomps so can only generalize based on a small selection of units I know of.
In my narrow experience, the japanese and non-japanese versions have used identical component values and tolerances on identical circuit board layouts. Same brand parts even if memory serves. They have sounded identical and perform identically once trimmers were matched (with measurements) and any possible problems were solved (like bad pots or jacks from use/age).
However there are sometimes revisions that change one or more components, ground locations, values, locations, and so on. Typically these have zero effect on the sound other than possibly lowering noise or something.
But anyhow, boss products, japanese or otherwise, should be nearly identical within the same product name based on my own personal limited experience looking at (and modding) of their circuits for many many years.
For electronic components I'd be surprised if the country of origin is different whether we're seeing a product built in china, japan, USA, or sweden.
