The P-38 had a few advantages over the Zero, but maneuverability definitely wasn't one of them, although later versions of the P-38 were pretty maneuverable with the use of partial flaps. The P-38 had self-sealing fuel tanks, significant pilot armor, longer range, was quite a bit faster, and dove much faster. For that matter, most American fighters were much heavier than the Zero and could dive faster. The preferred tactic was to get altitude on your opponent, do a diving hit and run attack, and then to zoom back to altitude. Almost any American pilot who tried to turn with a Zero was asking to get clobbered. Due to its contrarotating propellors, a P-38 could turn in either direction equally well. The Zero was pretty powerful for such a small airframe. It's turn rate in one direction (I think it was to the right) was significantly lower due to having to fight engine torque. American pilots were taught to turn against the Zero's torque if they needed to shake one, but diving away was even more effective.

Another big advantage the P-38 had over the Zero was much better firepower. Most P-38s carried four .50 caliber machine guns and a 20mm cannon bunched in a very tight nose mounting. The way the guns were mounted was an advantage over most other fighters because the rounds were all aimed to hit in a tight bullet pattern, doing massive damage to whatever it hit. Most single engined American fighters of the war mounted their guns in the wings. The guns were "focused" to concentrate their fire at a certain range, say 200-300 yards. If you were closer or further than the focus distance, then your bullet pattern was wider. P-38 pilots had a better chance of getting in longer range shots with tight bullet patterns.