Dobrý den, jak by se přeložila věta ,, Kéž by to bylo jako dřív." nebo ,, Přeji si, aby to bylo (mezi námi) jako dřív." Děkuji Vám a přeji pěkný den. 

Zkuste to sám s pomocí tohoto článku Přací věty (wish clauses).
S případnými úpravami Vám potom rádi pomůžeme. 

Asi bych řekl, ,,If only it was like before." nebo ,,I wish it was like before (between us)

Mohlo by byť… I wish it was like used to ?

I wish we could go back to how we used to be.

Po “I wish” je sloveso “to be” ve tvaru WERE u všech osob. → I wish it were like before.

Děkuji za odpovědi a rady

While I agree with you Lucka. Were is on its way out and was is also considered correct in everyday speech.

Another example is I could care less I couldn't care less is the right form and it makes sense, but you're most likely to hear the former.

Leave the subjunctive to Romance languages. of course were is more correct.

Considering the “Kéž” in the Czech original question, I chose the subjunctive which is still a correct possibility (and the only one if am not mistaken when talking about exams, school etc.). The colloquial English is , of course, something a bit different.

I would say that it was is now considered standard English as well.

http://www.bbc.co.uk/…itv301.shtml

Note that was and were are fully interchangeable with first, second and third person pronouns, singular and plural. Arguably, were sounds more formal than was.

To, že je něco informal neznamená, že je to hovorová angličtina.

Tady je hlavně také rozdíl mezi americkou a britskou angličtinou. V britské se v podobných situacích používá spíš was, pokud se nemýlím.