It’s not a totally unreasonable impression, but no, this will not turn into a second civil war. The Guard units of each state can be called up for federal duty. The National Guard is part of the US Department of Defense and thus ultimately answers to the DoD and the US president as commander in chief. The US military has multiple components, including regular services (eg the full time Army), reserve components (eg US Army Reserve) and National Guard components. The latter two are part-time military with one weekend per month training duty plus an annual training. Guards members and Reservists hold regular full time jobs.
The Guard units are deployable by the governors of their respective states, and so can be used in emergency situations like natural disasters. They have also been deployed against what have been perceived as riots that threaten lives and properties of the individual states.
However, they are subject to activation by order of the US president and they fall under the national command authority. Guard personnel take the same oath to the constitution as other military personnel, and cannot legally refuse federal activation. Guards personnel would be subject to courts martial and face potentially extreme penalties including being discharged from service under criminal conditions, being stripped of rank and benefits, and jail time in federal prison. This would be what we call a career limiting rule.
So, if push comes to shove, Biden can activate the NG and order them to stand down or to implement policies to maintain order. Thinking the NG units and in particular their commanders would disobey a presidential order because they just love their state governor and hate the president so much is getting into Turner Diaries levels of right wing apocalyptic fantasy.
I have to agree with the previous comment. I do not find this horrific or even disturbing, but very comforting.
Can you help us understand what aspects of this you feel some people might find discomforting?