Should I list talks I invited myself to give on my CV? I'm traveling a lot this summer, and I invited myself to visit and give talks at a couple of universities in other countries.

Do I list these talks on my CV? If so, under what heading? They're not exactly "Invited Talks." I don't have a general "Talks" section on my CV because I want to exclude conference presentations (which are already represented as publications, and which nobody lists in my field). I could have a "Seminars and Colloquia" heading, but people might assume these were invited.
Yes.

If you discover that a friend in a distant city is having a birthday party, and you ask "Hey, can I come?" and they say "Sure!", you've been invited to the party.

Same thing goes for talks. When the host institution agreed to let you talk, that was your invitation, which makes it an invited talk.

That said, you may want to distinguish plenary talks at conferences and formally organized departmental colloquia from random seminars run by individual faculty.