Difficulty bugged or am I bad?

You aren’t crazy. There are some fairly normal enemies and then there are definite bullet sponges. If they have a red bar under the white bar, they’re going to have ‘segments’ of health. You shoot one white bar off and you lose one segment of red bar. Most I’ve experienced so far have three segments to their red bar. And bullets definitely do less to those enemies too.

If you're on PC, there's a few configuration file tweaks you can do to make enemies less spong-y. Enemies gain 20HP per level in this game, and thus get very tanky, very fast. This doesn't change per difficulty. The damage scaling modifier does, but not enough to counter this.

I've set this to 5HP and increased how much damage I take as well. Feels much better that way, in my opinion. Legendary enemies still have more health, but not to an insane degree.

Do you want me to share the settings?

This game surprised me because I usually play games on normal to start, then lower the difficulty once it starts getting annoying, but I never felt the need to lower it here. It's highly dependent on happening to get good weapons and having a lot of ammo, though - I got pretty low at one point but ended up doing a lot of non- or low-combat quests in a row, which ended up giving me a lot of ammo and good weapons.

It's possible the difficulty settings don't work the same way anymore. Unless there's a guide on it you'll probably have to wait for more hard data to get out on how that stuff was handled this time around.

For me it's been take cover but keep moving. Get close and hit hard. Have med packs ready to use and don't be afraid to use the numerous buff consumables.

Do they have red bars under their white bar?

Those are legendary dudes. They have 3 fucking health bars and are also stronger and tougher than your average goons. Even on the easy difficulties, they are bullet sponges. And this is also pretty normal since Skyrim introduced legendary type enemies.

Personally, I pretty much only use Kore Kinetic weapons since they have the highest DPS. The MagShot revolver can practically 1 shot even legendary dudes 20 levels higher than you, and I have an instigating one so it does double damage if they are at full health.

Also make sure you pay attention to the level of the system you're in. The further you go from the start, the higher the difficulty gets. If you just took off to the outer reaches of the galaxy right from the start, everything is gonna be 40-50 levels higher than you, and even an easy enemy will be a strong as fuck bullet sponge.

I believe there's a mod that fixes spongy enemies.

for me it got better when I found a modifield malstrom with a long barrel, semi auto mode, and a small scope, this let me get accurate shots to the face without going through all my bullets like the grendal and half of them not doing much, another favorite now is the two shot shotgun, a double blast usually takes out everything but the dudes with the red bars

The enemies are bullet sponges. Thankfully it's easily fixed either with a mod, or by manually editing StarfieldCustom.ini.

Coming back to say, now that I've played the game, the game does not seem to scale with your level like other Bethesda games, each system has its own level, and they can vary wildly. Quests are not leveled independently and you may go to different systems of different levels within the same quest, so if you feel like it's really hard check if the system you're in is like ten levels above you or something. You can fight above your level but it's tricky.