I agree it looks like the top and down tubes are bent a bit.
The style of dropout to seat and chain stay connection and the style of the headset remind me of older Murray, Huffy and Roadmaster bikes. I believe that thunderbird front derailleur is from the ‘70s.
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk