Man, yobit should not be mentioned or referred in any situation. They participate in many routes of shadyness
Bitmex for up to 100x leverage as cruc said. (no USA)
Bitfinex can margin trade, no USA allowed though.
Binance is solid, tons of alts to trade and lots of USD-pegged choices like USDT/USDC etc to choose too. (no USA beginning in Sept 11)
long
list of bitcoin exchanges <-