Jim,
I don’t know how recognized a Euro note would be in a U.S. crisis, especially the premium of the dollar. (“Funny money” may even be assumed to be devalued, as if Canadian.)
The real concern about large Euro notes is that of presumed counterfeiting. A British friend recently told me that 500 Euro notes are essentially not legal tender for most commercial transactions, due to widespread counterfeiting suspicions. You can take them to a bank, but that is about it.
Unless you need to carry substantial wealth that will be put in an operating bank at your destination, I’d stick to dollars or precious metals. FYI: US currency weighs about one gram per bill. Which means that a stack of $20 bills is presently nearly “worth its weight in gold!” That means that gold over about $3000/ounce would be more portable (and far more compact) than our largest [piece of] currency. I prefer the more romantic notion of a vest with gold pieces sewn in. A man could wear a vest with nearly 400 one ounce gold coins sewn in (single layer) that would weigh nearly 30 pounds, and be worth about $250,000 at current prices. Now that is “bug-out wealth”! – Mr. Bravo