The challenge you'll find is that UK brokers aren't allowed to sell you US ETFs, HMRC-reporting or otherwise. That's another nice little bit of the catch-22: there's a piece of EU regulation that was written into UK law as part of Brexit, called MiFiD. The relevant part of that prohibits "marketing" investments to retail investors resident in the EU/UK unless they publish a Key Information Document - supposedly for consumer protection. No US ETFs (that I've ever found) publish such a document, and I understand there's a clash between the EU/UK rules and SEC rules that mean they can't follow the rules to publish a KID.
In practice, that means EU/UK residents find it very challenging to purchase US ETFs. There's nothing against the rules in you buying them, only in the broker selling them to you. And HMRC-reporting ones are generally good for UK residents, aside from the challenge of purchasing them.
Some workarounds:
1. The reason the presenter suggested a US broker is that they may allow you to buy US ETFs - IF they either don't care about the EU/UK rules, OR they don't know you're UK resident (i.e. you use a US address for the account).
2. There's a weird quirk where options on US ETFs are allowed to be sold to retail investors in the UK/EU, just not the underlying ETF. If you exercise the option to get the underlying ETF, now you own it, completely within the rules. Don't get me started on the stupidity of the rules allowing people to buy options (a far more risky and complex investment) but not these very vanilla ETFs. Biggest downside, aside from the faff, is that you have to buy in lots of 100 shares, which can be a chunk of change for some of these ETFs (100 shares of VTI would cost about $20k).
3. Get recognized by your broker (US or UK) as a professional investor under the MiFiD rules. Broadly speaking, you need to meet any 2 of 3 criteria: a) >€500k invested b) employed in investing c) history of active trading (something like 10 trades per quarter for the past year).
To answer your question in bold: PFIC doesn't care where the broker is located, it cares where the underlying funds are domiciled. US funds are good. Irish, UK, Luxembourg, etc. funds are bad. Theoretically, you could even buy European funds from a US broker - that's perfectly legal, just puts you in PFIC pain (unless you do it in an IRA - I do this as another workaround).