I'd point you towards polymarket (polymarket.com). It trades in USDC (a  cryptocurrency pegged to the US dollar), which you can acquire at various exchanges, like Coinbase or the crypto.com app. 

As far as reliability goes, consider that PM are a very new thing, so I recommend you use precaution with all of them for the time being.

Augur is working but last time I checked transaction fees were pretty high, so volume/liquidity was very small, it should improve in the near future especially if Ethereum transition to PoS (I also plan to start trading on Augur). 

I heard you can sometimes trade events on sites like BetFair.

Other current/upcoming Predicion Markets not limited to the U.S. are:

Gnosis

poly.market

Omen

FTX 

Guesser