@GeckoSerpent23 what you are describing is a permanent Solutrean Hypothesis. The Solutrean Hypothesis posits that Epipaleolithic (20kya - 10 kya) Western Europeans crossed over the Atlantic, settled in North America, modified their Solutrean stone tool technology to create the pre-Clovis stone tool technology, spread from the (at the time exposed) Continental Shelf towards the Pacific Coast, they passed their technology to the arriving Beringians, possibly interbred, and diminished into extinction as a separate and distinct people. The proposed Solutrean Americans' extinction was coincidental with the North American megafauna extinction. The archaeological and anthropological consensus currently rejects all this, though the idea is slowly finding more acceptance.
Epipaleolithic Western Europeans had no Caucasus Hunter Gatherer ancestry, and they are posited to have a different complexion compared to modern Western Europeans because they lacked the alleles for light hair and skin that modern Europeans have, though many of them had blue eyes. Speculation on the complexion of the Epipaleolithic Western Europeans varies from light tan to very dark. If the Solutreans did cross over, and assuming no subsequent changes in their physical appearance in sixteen and half thousand years, they would still look significantly different from modern Nortwestern Europeans. Judging from how the Gaunches were treated by the Spanish, and how various internal European Crusades treated other Christian Europeans then I think this would not be peaceful.
To survive the climactic changes of the period, the Solutrean Americans would have needed widespread agriculture and animal husbandry. Agriculture, and especially animal husbandry, are the natural laboratories of pandemics. Now assuming no changes to Eurasia, not only do the European explorers spread their unique Old World plagues, they also bring back New World plagues to Europe.
The terms Caucasian/Caucasoid and Mongoloid are outdated, they
were based on cranial morphology and on some doubtful and simplistic theories of ancient human migration.
Can you offer some alternate terminology to use, and the reasoning for it?