I`ll be adding all the US services and options and write a detailed review after this CoinMama situation is resolved or not and update here.
I am not from US, but I know Coinbase is the most popular exchange there.
I was able to transfer money from US to Bitstamp several times in the past, about 3 years ago. I never had problems with that exchange at the time. I don't know their situation now, but they are one of the oldest exchanges around and I never had any problems with them.
I avoided coinbase based on years of complaints and weak support commonly complained on this forum. I`m aware bitstamps long standing reputation in the past as one of the oldest exchanges to be around still, but I dont know if any US customers experiences so if anyone would like to share their recent experience that would be great.
Update: So CoinMama got back to me yesterday this message:
"Thanks! I've confirmed your wallet address. The order is now processing, and your coins will be sent shortly.
Keep in mind that once we confirm the payment the rate is locked, we do apologize for our response times, we are experiencing a high amount of traffic, but you are correct and we are working hard on a live chat option!"
The only reconsidered part in this situation is the rates are locked so you get what you paid for, so if you are not in a rush with coins then consider them, but downside to this is wallet confirmations are a hit or miss since apparently this is my first experience semi large amount of $500. I would send small purchases to see the wallet confirmation is responding to get your coins first before you take your initial purchase.
Conclusion:
I did get my coins but it took about total of 3 days 
to get since the volume of support tickets and covid19 situation where most are working at home, but from this small experience I feel they lack on the customer service side.. just as this "manager" admits not having a live option to chat or phone number which seems a common thing which is horrible in the crypto community when running exchange.
Important side notes: Imagine you purchase $20,000 worth of bitcoin only to get the same problem? I`m not pointing fingers at CoinMama, but its very possible that if someone chooses to gain money from this it would selective scamming after building up the reputation or known services that a company provides. Eg: not enough KYC documents other excuses they can claim all these stories and get away most legal claims or any form since they are already in another country.
Other US services currently trying:
1. CashApp - pretty simple to use and its owned by square, but so far the email support has no response.
2. Binance US - binance will lead you to another third party member such as simplex or another name I forget, but I started a transaction for $50 test to see and Simplexs system fails to get the uploaded selfie as the image to upload to continue getting a technical error so you wont be able to proceed. The only good thing about simplex through binance is simplex customer support responds right away asking you if you would like to cancel the transaction or continue to move forward.
3. Changelly - similar to Binance US i go through the process of paying USD to BTC or altcoin and changelly will provide your best options, but in this situation one of the third party they list their website "MoonPay" after verification their exchange on start this process reads as "error can not load" so another technical issue on the website itself.
