It's perfectly correct as a translation of the English, I've added it now, thanks for the suggestion.
This unit looks at the use of the imperfect that reflects time passing. 'Fuon ni' would be used to say things like 'Fuon ni ar y llong trwy'r nos? 'Were we on the ship all night?'
Although it's more natural to ask this sort of question in the second person eg
Fuoch chi'n byw yn America llynedd? Were you living in America last year?