2.) The United States is a state-nation whose constitution and founding principles are based on classically liberal norms and ideals. Any successful political party has to ostensibly base its policies on these essential principles in order to gain support within a country characterized by a high degree of civic patriotism. Liberalism is not a monolith, and there is a huge difference between social-liberal and liberal-conservative parties.
3.) Australia mandates that people vote. The United States suffers from the "voter fatigue" phenomenon, which is a direct byproduct of the volume, diversity, and frequency of voting opportunities in the United States. Switzerland suffers from the same problem and for similar reasons.