Operators from other countries will often use the QSL Bureau system to get cards to the US (or wherever).

Each state call district has a volunteer organization coordinated under the ARRL's direction to handle incoming QSL cards.

Anyone who is (or has been) active on HF should find out what their district's organization wants for incoming cards. Some want SASEs (typically 6x9 envelopes), some prefer funds. Regardless, unless they have something from you, there will likely be some incoming cards that you never get. And some volunteer will probably end up filing the cards for months or years.

Good reminder. I receive bureau cards once or twice a year.

Here is the ARRL page with the different regional contact info: https://www.arrl.org/incoming-qsl-service

I throw $5 at them via paypal about once a year, but they will also take checks (your region may differ in how they accept $). Every time they receive cards for me and forward them on to me via USPS, it uses up a dollar or two. My region has a web page where I can punch in my call sign and it'll show how much $ of mine they still have. When I see the number get lower, I know they will be sending me some bureau cards. I am happy to support this.

Don't you have to be a member of ARRL to use them?

Only for the outbound QSL's.

Gotcha.