Options for pre-paid cards ?

Hotels should eat up your cash fairly quickly.

Remember that if you move more than $10,000 or €10,000 value across borders you must declare it or risk having the money confiscated. European airports have currency sniffer dogs, and probably the US has too.

I'm sure that any US bank would have to convert your euros to dollars, and then you'd have to convert them back again in Europe, losing money on each transaction. I'd carry the large bills in a money belt under your clothes. Nobody will want to give you change for 100 on a small purchase (at least not in Italy), but if you're spending 75 on dinner for two, then it would not be unreasonable.

You can't load them onto a card in the USA because Euros are not the legal currency here. The only way would be to convert those large bills into US Dollars and then load the US Dollars onto a card.

You won't lose your cash if you put it in your money belt or your neck pouch. Take some Euros with you every time you go on your trips. Spend them on hotels - that's the quickest way to get rid of them like Nigel said. If we have a large amount of currency anywhere we pay for the hotel with it.

I used to pay my last-stop hotel bill with leftover euro plus credit card, but now I just keep the euro for the next trip.

I have used 100-euro notes at hotels, some restaurants, and when buying train tickets (places that are likely to have done a lot of cash transactions that day). Not so good for purchases that are small. Also, duty-free shops at the airport on your way home.

I'm not sure if this would be an option, but you could have a look at it......

https://usa.visa.com/support/consumer/prepaid-cards.html

As the others have mentioned, you'd most likely have to get your Euro converted to U.S. dollars to load the card, and you'll pay a price for that in terms of exchange fees (the banks always get their cut).

Thanks for all the replies. I think for now my best option will be to keep the cash in euros and visit some banks (will be in Germany first) to swap the larger bills for smaller bills. I have read that Bundesbank and ReiseBank in Germany both do this (sometimes with a small fee). And then just be really careful about not losing them!

Just how large a denomination are you taking about???

With Europe being more of a cash society than the US, spending even €100 notes is not that difficult. Most bars or restaurants have no trouble breaking them when you make a purchase. ATMs routinely give you €50's. While true you don't want to try and buy just a bottle of water with a €100 or €200 or €500, I don't really see a need to go to a bank to swap them for smaller.

I agree, you should have no trouble spending €100's so long as you use it for a large purchase (restaurant bill), and not for an €2 ice cream. I would not call €100 "high denomination", ATM's dispense €50 and sometimes €100.
You may have problems with €200 or €500, because they are relatively rare and not well known, but you should have no problem paying your hotel with them. Absolutely no need to go to a bank to change them.