I haven't caught dog whistle stuff at all, and the Viking reenactors I know best seem progressive. I only know my local area, but some of them talk about going everywhere, including of course the east coast and L'anse aux Meadows. So, I've kind of assumed it's a national phenomenon.

Leif Erikson is a big reason why the period is so popular, but there's also just appeal in berserk, mead-swilling sea warriors. Knights in armour are also a major thing. The WWII reenactors have guns and maybe some troop carriers, but it just doesn't have the same imaginative crowd appeal. Cost might also be a factor - a wood shield, an axe and a tunic is all you really need to play a Viking.