Knocking down the strawmen.
First, to characterize race-first White nationalists as people obsessed with 23andMe results (or who believe "Russians are the same as the Irish") is as much a caricature as saying all European ethnonationalists want to re-fight World War II. In each case, you can find some who fit the description, but hardly most, much less all.
See this on 23andMe and related tests
Even in the US white nationalism is failed as a concept. Cajuns, Alaskans and Minnesotans are not the same people.
If WN has failed it has been due to poor leadership and freakish fossilized dogma, not due to the fact that we haven't atomized ourselves enough! Two Alaskan families are "not the same people as well" - perhaps each family should establish their own micro-state (or igloo-state)?
There is a reason why your founding fathers created the united states and not a state.
America is hardly the same nation made by the Founders. Local identities ultimately fail in America because the USA is so heavily "diverse." Minnesotans can be Somalis. Alaskans can be Inuit. Christian Midwesterners can be illegal Mexicans brought in for a meat-packing plant. Boston liberals can be Jews. If you say then you are talking about White Alaskans and White Minnesotans and White Midwesterners and White Bostonians - well, yes, what do they have in common - race, they are White. In America, that's the glue that holds it all together. Without race, local identities can - and do - devolve in to cucked civic nationalism. Let all the "people of Houston" stick together in the face of a natural catastrophe! Whites, Blacks, Browns - they all got that "south Texas" identity, don't you know.
I would recommend white nationalists in the US to focus more on the regional and what makes them unique instead of trying to invent a bond between them and very different people on the other side of the continent.
European activists get frustrated with "uninformed Yanks" who "misunderstand Europe" and give "low-information advice." Well, that goes both ways. Imagining America as a big Europe while every other person (nearly) is a racial alien of some kind does not work. A White American who is racially aware (or at least not cucked) has much more in common with a similar White American "on the other side of the continent" as they do with cucked Whites, or non-Whites, who share similar local cultural markers and identities. If Europeans cannot understand the overwhelming importance of race in America and American history, then their advice is not helpful.
Also race isn’t really a necessary discussion in Europe since there are extraordinarily few Slovakians who aren’t white.
But it is absolutely essential in America for the converse reason. And is it really immaterial in Slovakia? I read somewhere they are headed for majority Roma status - I presume you don't consider gypsies to be White. And beyond that - in today's globalist society, the aliens are "just around the corner" - even in Slovakia.
Different people of European origin still need to stick together for the common good.
Eliminate the word "still" and you are getting it.