What exchanges are US users currently using to trade alts besides binance and bittrex?
Kucoin, Poloniex. There's also Coinbase Pro if you only want to trade about a dozen of the larger altcoins. Huobi also has a US site now (which I haven't tried yet) with a couple dozen altcoin markets.
I think Kucoin is the only option besides Binance that allows unverified accounts.