The ACA created a pretty strong incentive to limit hours to part-time (what was the cutoff? 30?).The issue with unemployment stats under Obama is that unemployed workers were dropped from unemployment stats if they had not found a job after one or two years. In many cases, baby boomers decided to retire rather than continue looking for jobs. I know many people in this boat. Therefore, I think unemployment is higher than 4% but is not as high as 9%. The economy is worlds better than it was in 2008-2009, but it has not seen much of a return of manufacturing jobs. Many service jobs have moved overseas.
My understanding is that most jobs created under Obama have been in the retail and service sector, and companies avoid paying benefits by not hiring workers full time. Companies used to hire full-time people but they don't bother anymore in order to cut costs. Companies like Walmart essentially use the US government to provide the health benefits they once provided.
It will be interesting to see how much manufacturing and full-time service jobs will return with lower corporate taxes and fewer regulations.
The thing about manufacturing is that the loss of jobs does not always mean "decline." Manufacturing output continues to climb while employment declines thanks to that good 'ole capital-for-labor equation. For those that get manufacturing jobs operating high tech equipment, it's great as wages continue to rise. But menial assembly tasks just won't work in the US unless foreign logistics costs, energy costs, tariffs, supply chain concerns, etc. just make it much better to source domestically.
Reforming the tax code will help, especially if companies can repatriate profits and invest that capital here, but I think the effect will be incremental at best. But if a town of 15,000 regains a factory that has 800 jobs, that's a huge deal for them.