US-person or not, money market funds are very much higher risk than T-bills, for a host of reasons.
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Can you expand on this please? Is it in terms of T-Bills are simply safer, or are there warning signs of money market funds at risk to break the buck?

Structural issues.

First, there is counterparty risk. A lot of money-market funds invest in short term paper of companies, not the same as the Fed. They have to reach for yield (= a bad thing) to cover their costs. Particularly true for anything but the very largest MM funds, as running costs are not proportional to size.

Second, there is structural risk. A lot of money-market funds (and "short term government bond" funds) don't invest only in what their name seems to imply. Some pretty dodgy stuff and complicated derivatives in some of them.

And lastly, systemic risk. If the fund has a problem, or the fund's sponsor, or your broker, whatever---if the poop really hits the fan, T-bills in your own name would be by far the safest (other than devaluation risk). T-bills at your broker slightly less so, but still better than money market.

To make matters worse, often the money market funds offer lower yields. So, more downside and less upside.

Jim