According to Census Bureau reports issued in September, 33 million people, 10.4% of the U.S. population didn't have health insurance coverage during 2014. 4.5 million of these uninsured were children. The reports show that most of these uninsured people could have had access to coverage under the Affordable Care Act or otherwise, but they chose not to sign up. FiveThirtyEight.com has great graphics and story that offers an analysis. The Census Bureau's Sept. 16 press release with links to its reports is here. Excluding immigrants and people in the "medicaid gap" who are low income but don't qualify for a subsidy, about 22 million people are uninsured and more than a third of them are young adults between 19 and 34.
The Census Bureau reports that in 2014, there were 46.7 million people in poverty (14.8%). The 2014 data shows no statistically significant difference in either number or rate from 2013 estimates, The percentage of people without health insurance coverage during 2014 was 10.4%, down from 13.3% in 2013.