What is keeping the U.S. economy afloat?

Our economy is vast. Business cycles excepted, the macroeconomy usually manages to run smoothly, at least in terms of providing enough growth to support its large middle class and enough innovation to keep things that way. No, the U.S. economy does not and could not run itself. We need government for many reasons, like stabilizing and regulating the economy, and providing things private markets don't, like universal pensions, national defense, mass education, and a safety net. We must trade and invest with the rest of the world, let in some immigrants. Etc. Yes, our economy also creates and/or cannot solve big festering problems. Like growing income/wealth inequality that leaves too many with too little and a tiny few with vast wealth and political influence, maybe close to beyond what a democracy can thrive alongside. For my entire adult life, our economy has lurched from one huge investment bubble/capital misallocation and crash to another. Separately the costs to regular Americans of the major building blocks of socioeconomic mobility and even stability - notably higher education, health insurance, and housing - keep rising, even when "inflation" is low. Our politics have become wildly dysfunctional, dominated by billionaires, and is (YMMV) currently in the hands of incompetent extremists. Seeing is believing. It makes ones wonder: What is keeping the U.S economy afloat in these bubbleicious times with all their political and global uncertainty?