Unless something more material like a whole continent turning anti-imperialist, if not socialist, and deciding collectively to nationalize the fruit and veg produce, and thus disrupts U.S's produce imports -
I don't think any internal problems in America would reach to a boiling point, as to end on a conclusive note
So what if it's a big deal to you, huh, America is the most armed-country, and has a lot of guns, yet no civil war(s) has occurred recently... it's just reactionary settler business as usual
Im America, nichts neues
I also expect that economic conditions will ultimately serve as the primary catalyst for internal strife. Incidents such as the attempt on Trump act as catalysts that exacerbate tensions, and that can escalate into actual civil unrest. Another contributing factor is the pervasive mythology of American exceptionalism which is essentially a religious doctrine positing that the US is essentially a perfect nation. Consequently, any issues arising within the system are perceived as external threats rather than inherent flaws. This mentality fuels the polarization between mainstream Republicans and Democrats, much like a religious schism. Both sides view each other as heretic traitors intent on destroying the nation.