First, I'll answer your question. Then I'll give you G-R-E-A-T encouragement.
the easiest song I know consist of three chords, which is really only one chord (if you play full chords) moved up a half note at a time., It's called "Bald Headed Woman". If my memory serves me correctly, it was played by the Pretty Things. You can play it in any Major key you like. If I remember correctly, our band played it in G.
Another very easy song is "The Rose". Again...three chords, and very easy strumming. You can get by with playing it with no real rhythm.
But NOW...HERE"S the great news. Learn 8 chords in one key, and you can play thousands of songs. It's true. In the key of "C", those 8 chords are: C C7 Am Em F Fm D and G. The o0rder to put them together depends on the song. But as yoiu play these chords and L-I-S-T-E-N to the sound of each...and listen to the song you wish to play, you can see how each chord will fit in. The more you play, the better your "ear" will develop.
Now...an additional encouragement: If you learn to play these 8 chords as FULL chords, you can play in ANY KEY, simply by moving up the keyboard by half-notes.