Two problems, one substantive, one propaganda.
Since the 1980s liberals in the Anglo world have been less effective at propaganda. This is partly because media reportage reflects media interests, which are usually conservative. This manifests both in news pages- choice of issues to cover, slant, sources, recurring tropes and so on. Also, I think, American liberals seem to be just ineffective at selling their ideas, while American conservatives are extremely effective. Compare Barack Obama to Ronald Reagan: imagine if Reagan had assassinated an Osama bin Laden metaphor. That would be how we would remember his presidency. With Obama, we remember bullshit like an attack on an embassy. George Bush managed to stifle all debate for over a year; no Democrat could ever achieve that, regardless of circumstances. I'm not sure why this is, but it is a severe problem and it must be addressed. People are more likely to believe lies out of a Republican's mouth than the truth from a Democrat. Fix.
Problem two: the US system is actually written in a way that tends to prevent progressive change. This is partly because the Republicans have effective party loyalty, but the Democrats do not. While that is true, Liberals can't really win. When Republicans initiate some unbelievably radical change- so, the invasion of Iraq- all Republicans vote aye, not enough Democrats vote nay and the filibuster is never considered. How many major, controversial laws were passed by the Bush administration- and that's one of the most incompetent governments in a generation? A dozen? Two? The filibuster is not a weapon against regressive change. But think of the effect against Obama. Even extremely uncontroversial policy everyone agrees with- say, Obamacare- takes months or years to pass, chewing up all other time. The result? Obama has one major legislative reform, has not rolled back any of Bush's crap, and faces the repeal of that single reform if the party loses.
Now how is the system written wrong?