2003 Nissan Frontier front passenger side wheel

I'm pretty sure you have torsion bars for front springs. Those are adjustable and they often sag from age. It's easiest to adjust them up when the vehicle is raised off the ground, but you have to set it back down and bounce it before you take measurements.

The people at any tire and alignment shop will be able to tell you where to take the ride height measurements and what they should be. They have small books that show that for every car and truck model. Correct ride height is critical for proper front-to-rear brake balance, steering response, and especially tire wear. The wheels can be adjusted during an alignment so the numbers look good on the computer screen, but tire wear will still be bad if ride height isn't right.

If you have coil springs on the front, most likely one is broken. If it broke near the bottom, as they typically do, you may not be able to see it easily. You will have to feel it to see if it's in two pieces, but be very careful. A broken spring almost always has real sharp points on the ends of the coils. Just move your hand slowly to avoid getting cut by those ends.