I tend to agree with OP that US stocks are significantly overvalued, but who am I to argue with the market? Bubble? Possibly, although it can be argued that all bull markets eventually end in a bubble otherwise they wouldn't end.
I'm not a TINA advocate, though. If you think it's expensive then you don't have to buy it.
I tilt my portfolio towards value sectors, so for me I am:
underweight US
underweight fixed income
overweight dev international stocks
overweight emerging markets
overweight real assets & resources
100% VTSAX? I'd rather slit my wrists.