Well, no Norwegian, Swedish or Danish are spoken in Normandy, Sicily, Russia, Dublin or the Danelaw. For whatever reason (low numbers, inferiority of the written culture, I do not know), Vikings/Norsemen did not seem very interested in speaking with natives or spreading their languages. I know there are Scandinavian loanwords in English and place names. It would surprise to me if Gaelic would not have loanwords from Scandinavian languages (via Ireland or the Scottish isles).
It did indeed. And reasonable numbers of Scandinavians settled in what became Scotland. Places like Dublin, at one point, were almost wholly Scandinavian. But for whatever reason, their language disappeared while Gaelic soldiered on (although English has now largely killed off what remains of Gaelic save in certain specific areas).