In general USA post takes the longest inside the states - ie from one side; say NYC to LA. It takes even longer if its from /or to Lower Butt Pane South which has no major airport hub. Once its on the plane here - its pretty much straightforward unless its a shipment of Tomato cans from California that contain cocaine - then it will get held up. In general theres no advantages with USA in getting anything but plain old slow parcel post - mostly it gets here just as quick as the spiffy speedy offerings.
UK is marvelous - I'm sure we have all had the experience of bleary eyed clicking around tired a late Friday, or as blahman -hyped up and loved out on EXXY@ 3am friday/sat morning clicking big-time on-big timer shoes then seeing shoes arriving on Tuesday in the wrong size, wrong colour. Try to remember what and why you ordered. Explain to partner why you are getting expensive shoes from overseas each week which all look the same.
Swiftly think up explanations to partner for $600 + worth of shoes that , to the normal eye, well to any eye really, look similar, "Ahh honey - looks like the computer went crazy and they sent me two pairs of this stuff" - Oh well I'm sure someone else will buy them off me - you got Gerry Nelsons number there luv?"