Why? How? The US balanced the budget under Clinton. I was pretty young, but I don't remember the standard of living collapsing in the early 90s (quite the opposite in fact).

for a few years only, and with tiny surpluses compared to deficits that came before and after. and the deficits exploded again.

I can hold my breath for a few seconds, but not for a 10 minutes. it is like that.

and that is only the federal deficit. local governments are also running massive deficits.

I mean, the CBO has a range of policies for fixing the federal deficit, most of which are pretty reasonable. I'm a fan of taxing the better off more (but I'm not a US citizen or taxpayer so that's easy for me to say).

Define "the better off?" I also agree with you in principle, but you're overlooking an important fact about American politics. The mainstream "left" in the U.S. is dominated by affluent professionals who hate paying taxes as much as any Reagan Republican. They pay lip service to the idea of "taxing the better off more," but by that they mean "billionaires." That's not a big enough tax base to raise the $1-2 trillion we would need to fix the deficit.

That's why you get a ridiculous situation where even the center-left party is promising not to raise taxes on people making under $400k/year. In reality, such a tax plan wouldn't even meaningfully raise taxes on people making $1 million a year. You can't solve the deficit by raising taxes if you're unwilling to tax 99.5% of the population.

How much smaller would the US deficit be if America wasn't invading multiple countries at the same time?

Taxes are only one side of this problem. The other side is expenses. Empires are expensive.

Which countries are we currently invading? Regardless, in the 2023 budget Social security far outstrips defense, Medicare is just a shade higher, and Medicaid is not far behind. I'm entirely in favor of slimming down the US military industrial complex, but doing so isn't going to fix the deficit. You could 0 out the defense budget entirely and there would still be another trillion dollars of deficit to deal with.

Just listing the ones from my short life so far: Afganistan, Iraq, Syria, Libya, Palestine & Lebanon (indirectly through massive support to Israel). I'm sure I missed a few since there are so many.

This is entirely correct. I've disagreed with you a bunch over the last few months but this is unfortunately true.

I do think that, at least, removing the income cap on social security would be helpful.

Honestly though, the only thing that'll stop the current US approach to fiscal policy is the bond markets.