BRU has the "normal" setup for transfer passengers for airports in the Schengen area: passport control if you go from Schengen to non-Schengen or vice-versa (so not for you) and security if you arrive from a non-Schengen country (so you do need to go through security).
The airport's website is a lot clearer and even has some videos showing you the route to follow. Note that flights to the US can also leave from the "T" pier (at the end of the A pier - which is normally the "Schengen" pier). There are buses between "B" and "T" so that transfer passengers don't have to enter Schengen.
https://www.brusselsairport.be/en/pa...ransferringpax