In the US I use Delta Sky Clubs, Centurion Lounges or Priority Pass lounges as I have access to all three. I will try the AA lounge in LAX sometime, thanks for the recommendation!
I am guessing that's from the AmEx Platinum card? If so, you need to be a bit careful when it comes to lounge access. To be exact any of the three airline lounges agreement AmEx has (for those keeping track at home it's
Virgin Australia, Delta Airlines and Lufthansa) requires you to be flying them to access their lounge. So if you hold a Qantas ticket, you can't simply flash your Platinum card to get in. You need to be flying Delta (even Basic Economy for the time being will do). Similarly presenting a Qantas ticket and a Platinum card at a
Virgin Australia lounge won't get you in. You need to also have that
Virgin Australia ticket. Additionally, some airlines have additional benefits. Specifically with Delta you can access their lounges on departure and arrival on a Delta Airlines flight.
Another point, the number of guests you can bring in will vary depending on the lounge and the type of Platinum card you hold. For instance, for Centurion lounge access if you hold a US Platinum card you can't bring in any guests for free (unless you spend $75K+/year on the card). However, holding a card issued elsewhere you can bring in 2 guests no problem. Plaza Premium is 1 guest (I think) whereas with Delta it's 0 guests.
The last thing I'll point out is that the AmEx Platinum lounge program is extensive and complicated. Your best bet is almost always to use the AmEx mobile app which has as a feature a handy lounge guide which will show you which lounges you can get access to. It's not just Priority Pass, Centurion or airlines lounges either. It's a number of smaller lounge collections in regions where Plaza Premium has weak coverage. It's also Plaza Premium too. And for those at home saying, well isn't Plaza Premium part of Priority Pass now? Yes and no. Yes it is a lounge you can visit with your priority pass (be it issued by AmEx or elsewhere) but no you don't get the same benefits as an AmEx Platinum accessing the lounge with their card. To give you a very specific and relevant example, consider the international arrivals lounge at Sydney Airport operated by Plaza Premium. If I show my Priority Pass card, I'm given two hours to use the lounge with showers costing extra. However, if I show my Platinum card the shower is free and I get three hours instead (not that you would necessarily want to spend 3 hours at that small buffet area). And I can say this as someone having made the mistake of flashing my AmEx Priority Pass card instead of the Platinum card and having the lounge attendant correct the "error". And trust me after a 14+ hour flight from LAX in coach you want to have a shower!
-RooFlyer88