Sales to liberals and conservatives are nearly split 50/50. That comes from personal relationships with the top gun dealers in the country. Don’t be fooled into thinking the left isn’t well armed. The left has also been joining the military at high rates, many specifically to gain combat training.
Don’t let bravado lead you to seriously underestimating the opponent. We may be better at it, but they haven’t fielded their A-tream yet.
During the first Civil War roughly 1/3 of US officers joined the Confederate army, like RE Lee, about 1/3 were loser Democrats like McClellan and only 1/3 loyal, war winning Republicans like Grant.
No reason to think it would be different in a CWII.