Yesterdays enemies are tomorrows allies.
Things change over years and decades, political alliances change and things you'd never expect countries to do, they go and do. Hell, look at Terminator 2. They had a line that went along the lines of "Why attack Russia? Aren't they our friends now?" That was just after the Cold War ended and the USSR dissolved. Put that in context of today and you'd get weird looks from everyone if you put that in a blockbuster movie.
Trying to make allies all over the world is smart and even if they were opponents for the last few decades, it's always worth trying to be friendly as you never know how it will pay off. It doesn't matter how big you are and how powerful you are, everyone needs friends.