The irish immigration surged in the 1800s because of the Irish Potato Famine 1845-1849. Most immigrants landed in New York. Because of their Catholic beliefs, most Americans did not welcome them, still reminiscing on bad times with the Catholic monarchy.
The Vikings eventually settled down in the lands they had conquered. By 950, the Vikings had stopped raiding in Ireland and developed instead as traders and settled in the lands around their towns. The Vikings in England largely became farmers and fishermen. The Vikings left many placenames in Ireland including: Dublin, Cork, Limerick, Waterford, Wexford, Strangford, Leixlip, Carlingford, Youghal, Howth, Dalkey and Fingall. A few of their words were also adopted into the Irish language.
Hahaha! No offence intended. If anything, I've learnt in recent years that some words we "correct" US citizens for, are actually closer to the original English than the ones that have evolved in England! :-)