1 iTunes account, different country stores

Hi.
I live in US but I'm of European descent.

I have an US based iTunes account established with music, videos, apps...
Sometimes I listen to internet radio streamed from Europe and I like the songs there, and they are not in the US iTunes store.

1. Is there an easy way to sign into another country store (right now I figured a way to click on a link on a web page and I'm prompted to create an account).

2. Is it possible to have an iTunes account which spans multiple countries?

3. If #2 is possible and I purchase something using another country store will I be able to download it to my iOS devices? Will the different stores purchases intertwine across the globe? As an example on my iPad if I'm signed into "the store" as I can't choose another country, be able to download music from abroad?

4. Will I be able to access all of the purchases from different countries using my US based account on my Mac living in US?

Thanks.