Boy, there are more great 2-siders than I remembered! Looking at the personal G-100 I came up with on the old forum, I'm thinking my own U.S. top 5 would resemble:
Dean Carter "Jailhouse Rock/Rebel Woman"
The Dovers "What Am I Gonna Do/She's Gone"
The Human Expression "Optical Sound/Calm Me Down"
Things To Come "Sweet Gina/Speak Of The Devil"
The Mods "I Give You An Inch (And You Take A Mile)/You've Got Another Think Coming"
with things like The Illusions & The Stoics bubbling under. Others that haven't been mentioned but I think are exceptionally worthy include The Tasmanians "Baby/Love Love Love," The Shy Guys "Black Lightning Light/Goodbye To You" and The Rogues "You Better Look Now/Train Kept A Rollin'"