The HTC One is already available in the USA, or to be precise Amazon.com, for as low as US $799.97 plus shipping.
Amazon.com is currently listing the unlocked HTC One at various prices ranging from US $799.97 all the way up to US $1,179.99, depending on the seller. The lowest priced, US $799.97 plus US $4.49 for shipping, can actually be ordered right now and that seller promises to deliver it in one to two days time.
As you already know, AT&T and Sprint will also have the HTC One 32GB and both want US $199.99 plus contract for it. Both carriers claim that it will start to ship out on April 19th. T-Mobile USA will also ship the HTC One on April 19 and wants US $99.99 on a US $20 per month two year contract.
Of course, we are not talking about the HTC One 64GB Developer Edition that will cost US $649 and should also be available on April 19th. Obviously, the HTC One 64GB is a better choice as it actually ends up cheaper than what Amazon sellers want for an unlocked HTC One 32GB.