Adam Lambert -- Back in the US of A [VIDEO]

Adam Lambert and his Finnish reality star boyfriend Sauli Koskinen returned to the States in time for Christmas yesterday ... just a few days after the pair was arrested in Finland for fist-fighting each other outside a gay bar.

Lambert and Koskinen weren't chatty -- but the warm and cuddly Xmas pic they posted on Twitter yesterday seemed to suggest things were now just ducky.