Hello,
A collect call can be placed by dialing a toll free number (also known as freephone in some countries) and asking the operator to place the call for you. This is how you can place this type of call when trying to reach the US from other countries as well. The problem with collect calls dialed from abroad is that all countries have different telephone systems and some don’t even have an operator assisted service you can call to connect via reverse charge. Honestly, I just spent a few minutes looking for the operator assisted number for Spain and couldn’t find it.
A second option you have, in case you want to contact a bank for example and they also provide you with a toll free number to call from within the US – either use Skype to call the toll free number (you will generally be able to easily find an Internet cafe in Europe where you will only pay for Internet usage) or use the instructions we give on the page below for dialing a toll free number from abroad:
https://www.howtocallabroad.com/qa/toll-free.html
Here’s a helpful article written by a NYTimes journalist on this matter (be sure to also read the comments at the bottom, they are quite informative).