According to Gallup data, the uninsured rate under the Affordable Care Act (ObamaCare) rose to 13.7% in 2019 from a low of 10.9% in 2016. This seems to be due to changes to the ACA under the Trump administration.
The most obvious change is the change to the mandate to get coverage or pay a fee. Starting in 2019 the fee for not having coverage is zero in most states.
So, some of the rise in the uninsured rate can be chalked up to people electing not to have coverage.
Still, about 7 million adults who had insurance under Obama now don’t under Trump, and that is a big difference.