Yes and no. If you order your "gold kit" off of an ad aimed at boomers worried about losing their houses, it is probably scammy.
If you're very rich and worried, you could stash away a bit of bullion at your home. You'll have other things of value you could trade on the black market of total societal collapse before you'd need to tap into that resource. If you're not very rich, a gold bar is not going to do you much good because it's a big chunk of change tied up in one item. You're more likely to need smaller denominations, like coins or rings, to pay for stuff in the apocalypse. Or you need to learn to smelt metal. The scam of it all is that people with a financial interest will advertize gold as the safe resource in times of high perceived crisis when the price of gold is already high or rising. It makes much more sense financially to watch the market and buy when it's down.
Gold is also something that needs the economy to come back before you ran out of other stuff to barter with. If our apocalyptical total collapse lasts a long time, gold will not be as valuable as drinking water, food, or shelter. Smokes (incl. vape juice) and booze might be more useful for a longer time.
I'm not rich and I'd sooner go down the prepper route than buying gold.
That depends on when it will break out. If it's tomorrow, China and Russia will be buddies or at the very least will be in a non-aggression pact situation. Most of Europe will side against Russia but might be more mealy mouthed towards China (even if they decide to start it by going after Taiwan and that escalates from there). The US will, as it is tradition in a world war, not enter until much later or unless attacked first. And on whose side? Depends on one person's bowel movement on that day an no longer on treaties and commitments. One of the many crucial areas to watch will be if the US honors the security alliance with Japan.
I say it depends on when because if we give it another 25-50 years, attitudes may shift. The US could try going for a more sane leadership and affirm its NATO membership. Sentiments towards Russia may shift in Europe, especially if the US is progressing further towards Idiocracy.