I've tried hundreds of beers in recent years. But it starts to get expensive buying some beers less accessible online. Is there any site about swapping beers between people of different countries?
Check out BeerTrade. It's not specifically limited to swapping between countries, but there is no reason you couldn't organize something there. There are about 10,000 people watching that subreddit currently.
BeerAdvocate has some swapping features including the ability to create a "want" and "have" list of beers.
You can try on BeerRate forum.
In the US, it's completely illegal for regular people to ship alcohol through the US Post Office inside the US. You can if you are a certified wine/beer/spirits shipper through UPS or Fedex or get someone to do it for you. That just inside the country! I am a certified shipper for my (defunct) winery and I've tried shipping wine internationally several times and it was so expensive we all decided not to do it. You can do it under the table (illegally) but I'm not sure it's worth the effort.
Pretty sure it's much easier in the EU.