But then there was this: https://twitter.com/NatSecGeek/status/1273329710576152581
https://www.csis.org/analysis/rise-far-right-extremism-unite...
https://www.americanprogress.org/issues/security/reports/201...
https://www.nytimes.com/interactive/2019/04/03/world/white-e...
https://www.theatlantic.com/ideas/archive/2019/01/homegrown-...
So right wing terrorism is a greater threat, unless you are worried about being killed.
But if asked "Are you more worried about right wing or islamist extremists?", my answer is "Yes".
Whereas something that is well known and homegrown in the USA (Timothy McVeigh, anyone?) has had a much lower level of concern assigned to it until very recently.
I think two "issues" are the relatively better protection against surveillance US citizens have (I wouldn't think it's an issue at all, hence the quotes) and the fact that they tend to be lone wolves more than Islamic terrorism, which often works through networks.
So it's not that easy to spot people like McVeigh, Kaczynski, or outside the US Breivik, before they act.