Following a promising second place in Saturday morning's sprint, Hamilton faced a recovery race from 18th on the grid.
But the seven-time world champion initially failed to make much progress on his soft tyres, rising to 15th before moving on to the medium compound.
He said his car had so much understeer during the first half of the race that he thought something was broken.
"I thought maybe at the beginning I tapped someone because I have never had so much understeer in my life, so I was turning in at slow speed and waiting, waiting, waiting," Hamilton explained.
"I thought I had damaged something like some of the others because there was debris going everywhere at one point but it was just the set-up that I chose.
"With better decisions on set-up, maybe we would be around where George [Russell, who finished sixth] is but we just have to keep fighting."
Commenting on his short attempt to make a start on softs pay off, he said: "Oh my god, I was the only one, I think, on the soft and it fell apart after lap one. It was very difficult."
Hamilton passed a few more midfielders and benefitted from the clash between Lance Stroll and Daniel Ricciardo to claim ninth. But he hopes upgrades planned for Miami will give Mercedes a much-needed boost in its fight with Ferrari and McLaren.
"It definitely wasn't better than expected. We expected to be somewhere around there," he added speaking to Sky Sports F1.
"Hopefully we have some step forward coming in next race. Until then, we'll be back in a factory next week trying to position the car better for Miami and hopefully we have a better weekend."
Russell said his sixth place was about as good as could be expected after struggling to keep up with both Ferraris.
"This weekend, we know where we're falling out," he told Sky Sports F1. "The last three races we were kind of in the battle with Fernando and [Oscar] Piastri as well. P6 is where we are right now.
"It was an interesting weekend managing to have two different set-ups on the car between Friday and Sunday. So, some info to go through but ultimately we just need to dig into the data and just keep on adding performance to the car."
