Yep, that's exactly what will happen. The CFTC already finex Bitfinex $75k back in 2016 for failing to register as a Futures Commission Merchant (http://www.cftc.gov/PressRoom/PressReleases/pr7380-16), but I can't imagine what kind of shitstorm will be kicked up when the USA goes after them for counterfeiting USD via Tether.

There is a slim possibility that Tether is in fact back by USD if Bitfinex is exchanging received bitcoin and/or other cryptos on regulated fiat exchanges like Gdax and Bistamp, and then wiring that USD back to their secretive offshore bank accounts.

If I were Bitfinex/Tether and I didn't have access to USD via normal banks, that's exactly what I would be doing.