It depends on how far the target is behind the obstruction. If the obstruction is light, and the target is very close behind it, then typically no problem. Target very far behind means a likely miss or worse.
From my own experience:
20 years ago, I was shooting a 600 yard High Power Rifle (NRA) course. I was using match ammo with 168 or 172 grain bullets in an M1 30-06. About every 4th shot was completely off the paper when the others were scoring 8 or better. It was driving me nuts. I finally realized that just a few thin wispy strands of cheat grass were in front of my muzzle about 10 feet out. (Cheat grass is probably less than a millimeter in diamether). You couldn't see the grass through the peep sights. Most of the bullets got through without hitting, and scored a good hit. Those that hit a single piece of grass would miss a six foot square target board 600 yards away.
Later, I took a defensive rifle class that involved a brush walk looking for hidden targets (IPSC type). I found a target (top third exposed) positioned immediately behind a large stump that had sprouted several shoots or saplings making a very effective brush screen. I fired my AR15 (55 grain FMJ ammo) at that target 6-8 times because I was worried about bullet deflection. Some of the bullets impacted the decaying stump top, other hit the brush limbs, but all hit the target because it was so close behind.
Over the years I've read at least two articles that tested various rifle calibers against simulated brush (constructed of dowels placed in a uniform array) with targets placed behind. The results were the same in both tests. The so-called brush busting calibers with large heavy slow bullets didn't do any better than the light fast calibers. All were deflected about the same, with a slight edge to the faster calibers. There are no great brush busting calibers.