I have no idea why I'm entering this fray but here goes:
Bernie Sanders or Donald Trump will not become president. Stop the fearmongering.
Bernie Sanders is not the second coming of Lenin. He's basically a Helmut Kohl-style social democrat. There's quite a bit of difference between the two.
If either become president, they're not going to destroy America. They can't just snap their fingers and raise tax rates to x% or build walls here and there. America is successful because of a great system, not because of great politicians.
The difference between southern Europe (poor economies) and northern Europe (doing better) seems to have more to do with labor regulations and the Euro rather than high tax burdens. The north actually seems to have slightly higher tax burdens, yet also stronger growth.
All that being said, 90% is probably too high a marginal rate. When Johnson (not Kennedy, the only thing Kennedy could get through was his junk into other women) put through the tax cut lowering rates from 90 to 70 in 1964, the economy roared forward (after a period of stagnation) at China-level growth (8 percent or so) for quite a few years. The poverty level dropped from 25% to about 15%, which is where it is now.
My guess is that most of us on this board are reasonably prosperous and are not struggling to put food on the table. Have your lives been affected by who the president is? I seriously doubt mine has. Certainly you want a president who will do the best job, but it's quite unlikely that any one president will ruin anyone's life. Most of that is up to you. Again, this country works because of the system, not the president.