Not much doubt Vikings were in pre-Columbian America. But the significant European DNA in Native Americans seems to be from at least 10,000 years ago, as far as I’ve heard.
The Viking’s ancestors were still cowering in caves in France eating primitive cheese, surrendering themselves to the Younger Dryas and picking lice when those Europeans, the Sa’ami, made it to America, East Asia, South Asia, Africa, and everywhere else!