While there is broad support for civilian access to firearms, there is also broad support for regulation like universal background checks.
Obama has
repeatedly pushed Congress to pass laws for various gun control laws.
Congress refuses to pass them, because the NRA has legislators by the... bullets.
They are a small, single-issue group with a dedicated and activist membership, lots of money, and expert lobbyists. Since we are in an era where small numbers of voters can mean success or failure, NRA voters have a disproportionate influence.
Fun historical note! This is also how Prohibition got passed. The Anti-Saloon League developed the tactic of focusing strictly on banning alcohol, endorsing anti-alcohol candidates, and attacking pro-alcohol candidates. This allowed them to ignore party and partisan divisions, and they often tipped the scales in close elections. They also gamed the system in other ways, such as pushing for an amendment before major changes in congressional representation kicked in, and they even unconstitutionally pushed to skip the 1920 reapportionment for the House of Representatives.
IIRC: After Sandy Hook, the NRA was briefly willing to play ball, and were somewhat involved in negotiations with various legislators on a UCB bill. However, a few extremists took the attitude that allowing
any law with
any kind of gun control was utterly unacceptable, and pushed the NRA to the most extreme position possible. As a result, they torched a well-known loyal NRA supporter (Patrick Toomey, who had an "A" rating from the NRA) for daring to work as an intermediary between the NRA and Congress on the bill.
http://www.nytimes.com/2013/12/15/magazine/inside-the-power-of-the-nra.html
We should note this is the kind of thing that the Framers warned about, and did not want, in the Federalist Papers. The inability to pass something as popular as universal background checks is a failure of our electoral system. Obama's executive action is him basically throwing up his hands, saying "I'm doing everything I can do," and putting pressure on Congress to listen to their constituents.