Democrats welch on their side of the bargain once they get what they want.
That's pretty rich considering the recent history of US republicans, led and symbolized by Donald Trump, the greatest welcher in our history.
Republicans fully expect that once the Democrats take control of congress, the wall will get defunded, we'll have several million newly-legalized immigrants
You mean just like Republicans took control and defunded the ACA but left in place millions of dollars of corporate subsidies for insurance companies? You're channeling Trump again, accusing democrats of doing the very thing that republicans are most recently guilty of.
who place a large net burden on education, law enforcement, infrastructure, and social services.
Except that new immigrants pay more in taxes and economic productivity than they cost. Our country has a net negative birth rate, we absolutely need new immigrants to keep our economy functioning. Cutting off immigration will result in Japan-style demographic crisis. I can't believe anyone still argues for this.
Or, the Republicans want no new regulation, the Democrats want more regulation, and the compromise is a shift to the left.
Except republicans have been cutting (mostly environmental) regulations at an unprecedented rate, so the shift is not at ALL to the left. There was a recent headline that says Trump's loosing of coal regulations is expected to kill an average of 1400 people per year, mostly in rural red states. The stats on air pollution vs respiratory distress fatality rates are shockingly robust. He's literally murdering Americans so that coal companies can profit, and you're accusing democrats of moving us left?
Or on gun control, the Democrats consistently push for more, but when was the last time you saw any legislation removing ineffective/pointless/onerous gun regulations?
Trump signed the law allowing mentally ill people to purchase handguns. He literally let crazy people arm themselves.
Republicans in Congress passed a law removing a state's ability to regulate concealed carry permits, making unregulated CC legal everywhere. They called it "reciprocity" but in reality it means the most lenient gun laws in the country now apply everywhere.
Trump signed a memo allowing a "fugitive from justice" (a person with outstanding arrest warrants) to purchase firearms. He literally made it easier for dangerous criminals to arm themselves.
Those are all just from the past two years, and they are all examples of republicans moving the country to the right on the gun control issue, despite six(?) highly publicized mass shootings over that period. And yet you're worried about onerous gun regulations? From over here, it looks like we're making guns easier and easier to get, and people are dying as a result.
On infrastructure, Republicans say "we can't afford to spend any more"
Republicans are never again allowed to make any sort of budgetary argument about fiscal responsibility after the current administration ballooned spending while simultaneously cutting revenues. The TCJA was a deficit buster, plain and simple. At least the democrats wanted to raise taxes to pay for our current spending, instead of driving the country off of a cliff.
As for Republican ideas in the ACA, just because it includes some doesn't mean the law as a whole isn't a steaming pile of compost.
They could fix it if they wanted to. They have all the power now. Where's the replacement plan? Answer: there isn't one, because the ACA was the republican plan to begin with.