If I were a US citizen living in Europe, I would try to make sure to invest both in EUR and in USD, so when you get to the withdrawal stage, you can withdraw from the account that gives you the most value for money.
I think you've said before that your husband is not interested in investing. If he's experienced in tourism and you are in a part of Italy where tourism is a thing, buying a place to rent out sounds like a better idea than putting the money in a savings account. Italy is not known for it's strong economy or real estate market, but the tourist industry is not dependent on the Italian economy. In fact, during an economic downturn I think many European tourists are more likely to go on "cheap" holidays to countries like Spain and Italy instead of far-away destinations.
I don't know much about Airbnb but from what I've heard, local governments want to crack down on people using that website because many people rent our their residential properties and don't have permits, don't inform the landlord / mortgage lender, break health and safety rules, aren't insured, avoid taxes, etc. If you rent our a holiday home as a business, get all the permits and paperwork in order I don't think it's that risky. Airbnb would just be one way of finding customers. We have booked self-catered apartments owned by professionals several times now through Airbnb and we've had some really good experiences. I don't want to stay in someone else's home but I prefer to stay in a place that has a kitchen. If you are in a region where tourism is big, maybe there are some government agencies that can help you find out what kind of permits etc you'd need to arrange.
Renting out to tourists would be lucrative because the rents you can ask are so much higher than the rent you can get from a long-term tenant. According to google, privately renting out an apartment to tenants is unlikely to give good returns in Italy, so you'd have to be sure converting to a holiday let is legal before you buy.