No, it's not parties that are entrenched, it's laziness and complacency. America could have a viable third party, the status quo could be shaken. But it would require a bit more drastic measures than just canvassing and making YouTube videos. It would require an election boycott campaign to shake the legitimacy of your democracy (and with two parties that serve the same corporate master, just how legitimate is it in the first place?), it would entail a period of instability with perhaps something even worse than Trump emerging for a while...
But by and large, Americans are comfortable. Despite the economic downturns, despite the drug zombies in the streets, most Americans are not ready for the hardcore sacrifices that are necessary to drastically change a political system.
So you trudge along, always choosing between two piles of shit, carefully weighing which pile is a bit smaller and stinks just a bit less. And you say, this is democracy in action!
In 50 years, women will return to the rightful place in the home. And we'll all look at this and laugh at how silly we were being.