We have a uniquely-bad electoral system, which is why so much of this day-to-day stuff ends up so insanely dysfunctional compared to most other developed democracies, and we've had mass-media special interest propaganda running rampant in a way it doesn't elsewhere, since the 80s (loss of the fairness doctrine—which, admitted ickiness aside, did seem to keep things on the rails a bit—and deregulation of media outlet ownership leading to unprecedented, extreme levels of consolidation; hard to tell which of those is most responsible, since they both happened around the same time) and that propaganda's able to be unusually effective in part because of our bad electoral system.
The result is that as long as factions in favor of these shitty things can stay under one of the two big tents, they get the tacit support of all the rest of the factions under those tents, even if most of them don't like that first group of factions. "Of course civil forfeiture's bullshit, obviously it is... but I can't vote for a pro-choicer/communist/whatever!" et c. (and, yes, the effect is on "both sides"—it's why we hear a ton of noise from "no abortion ever!" and "zero restrictions until the baby takes its first breath!" while the majority of voters, who just want more-or-less what Roe guaranteed, get little attention)
So, our freedom to vote is even, arguably, quite a bit less-free than for a fair proportion of our peers, since our ability, in practice, to express our actual desires through the electoral process is much more curtailed than in most of them—though, obviously, that part doesn't apply to authoritarians states.
Highly unlikely in one election cycle. The parties control both houses, the presidency, the states and the locals almost completely.
Step one is stop voting for incumbents and seriously consider voting out incumbents unless they are really, really good; exceptional. The longer someone stays in power, the more power they get, the more deals they make, the less accountable they feel. It's good to get fresh blood and a fresh outlook every term too. Really the bottom line is we expect change, but we keep voting the same people in and those people serve for decades. It's almost an insanity.
Once the existing political parties are weakened by turnover, you can start placing third party people in there. Now is a good time too, the mainstream media's credibility is on it's heels and has less influence over elections than traditionally.
Most of the ground the mainstream media has lost is to absolutely whacko q-anon and alt-right podcasters and video bloggers and alt-news, which is not a great environment for third-party people, unless the third-party that you're trying to start is a christo-fascist movement.
So what prevents parties similar to the SNP and LibDems to get elected in the USA?
OTOH they also scared them enough that we got The New Deal. So. Mixed bag?