I'm sure it's too late, but just in case someone in the future searches a similar question--prepaid SIMs in Europe are much cheaper and without as many restrictions as in the US (generally no minimum terms of service or required monthly minimums). Most discount supermarkets have their own mobile "brand" which are in fact SIMs for major networks (O2, Vodafone, Telekom). You often get a starter essentially for free (you pay for instance 10 Euro for the set, get the SIM and then get the purchase price in prepaid credit). Many of the providers have (again in comparison to the US) very cheap packages (I pay 8 Euro per month for unlimited domestic calling and 4GB of LTE). International calling is not so expensive.

EU regulations mean that if you purchase a SIM in an EU country, it will work at "domestic" rates in other EU countries. But be careful if you transit Switzerland--this is expensive. But you can often get "Swiss" packages (a week of Swiss service at a flat rate, for instance).

New regulations have tightened security to prevent the criminal use of "burner" prepaids. You will probably need to do an online ID check to activate your SIM. but you don't need to be a European resident or have a European address to activate.