IMO Domestic extremism will remain a likely threat but will be a drop in the bucket compared to the extreme poverty and natural disasters on deck for the coming years.
It won't be right or left ideologies that drive domestic terror but a sense of hopelessness and irrelevance of the previous well off youth that soon will find themselves destitute.
So many young people have already given up and made the decision to not return to work, the Fed is signaling interest rate rises and food production has been on the decline for several years. I believe there are only two outcomes that can result from such a situation... Either a global depression or war...or both.
When millions of young people decide not to work for whatever reason, be it justified or not, historically their value in society is diminished and has resulted in many being pressed into war through malnourishment or mandate.