How much US exposure do foreign indices have? I'm assuming companies like Nestle, Samsung, HSBC or Toyota all do a sizeable chunk of their business in US markets?

If you're not completely lazy then learn what a covered call, covered put, or a strangle is. Checking your account daily and making some clicks here and there seems well worth the out performance of the indexes and lower portfolio volatility. Math and risk are your friend.

Different tax advantaged accounts have different rules but afaik most allow some of this

Meh I think going 100% US is not optimal. Meh diversification is crucial and one should prolly have some international stock in their portfolio. I feel 100% US is overboard and one shouldn probably include 10-30% international just for even more diversification.

I’m 30 and have roughly everything in equities (maybe like 2-3% in bonds- not sure why but I guess it lowers overal portfolio risk). I’m single so I feel the risk is fine to take. I feel general investing advice is a little too nitty. I mean if you are say 10-20 years from retirement, probably should start changing it to lower risk but someone 30-40 should be ramping up in equities to try to maximize gains early and really build up some capital. Just based on past market trends, the market isn’t going to be bearish for a super long period so I feel being too cautious is a way to leave money on the table.