Yes nukes are a reason that NATO hasn’t committed ground troops to Ukraine, but geopolitical realities pertaining to trade relations with China, alliances with India, and Turkey being a NATO member state are way more reason that ground troops haven’t been committed.

Nukes are a non factor as far as us supplying materiel and financial support for Ukraine, Putin is not dumb enough to use them for any other reason then a Hail Mary if the very survival of Russia is threatened.