Trump shooter was a registered republican

What is known for certain is that this will galvanize the right in the US and lead to more rightwing stochastic terrorism in the long run.

This is like saying 9/11 fundamentally made the US more openly racist which is both true and false depending on how far back you look and what is the standard you take it from.

The US is a country which already children are killed in classrooms, where adults already die from all consequences of poverty and where mass shootings in general are already common.

Point being, things which could be described as "terrorism" everywhere else in the world are already common and some(most?) of these are already on a trend upwards. So it may turn out to be a mistake to think this is some special moment that defined those trends.