International roaming plans are getting more competitive. I think soon I will not need to get local SIMs in Western Europe.

I've done a few business trips in Germany this year, using Google maps for driving satnav, and combination Google maps and DB navigator for trains or public transport.

I strongly recommend the Deutschebahn app "DB Navigator" if you plan to use trains at all.

The total extra cost on my phone plan for using Google maps was next to nothing.

If using WhatsApp, remember that each account can only be associated with one number.

So you either have to create a new WhatsApp account for local SIMs, or use your existing account and it will appear as if you're calling from your US number even if using a local SIM. No big deal in practical terms.