1. I've never been to the USA.(Present Perfect)
I wanted to go there last summer, but I couldn't.(Past Simple)
2. His father came to London last Sunday. (Past Simple)
3. Lena has written a letter to Nick two days ago. (Present Perfect)
4. They've just bought some postcards. (Present Perfect)
5. I haven't seen Steve this morning yet.
6. I went to Paris in 2003 and 2006. (Past Simple)
7. Carol and I are old friends. I've known her since I been a child.
*Должно быть правильно.