that I haven't seen addressed anywhere yet.

Why does the GOP get to unilaterally decide what happens with the budget?

Is it that the budget has to be approved by both sides and the GOP refuses to sign, or is it that the GOP has final say over how the budget gets demarcated and they're refusing to sign until Obama guts the ACA? I'm confused as to why the Dems can't juut say fuck 'em and move forward anyway. Isn't the Senate majority Dems? Or something? That was possibly irrelvant but I'm not completely up on how American politics works exactly.