Hi There, my experience from working in the States then coming back home again tought me that in the USA they use NPT threads ( National Pipe Threads ) whereas we down in the Southern Oceans use BSP threads ( British Standard Pipe ), the two look very similar but in fact they are very different and do not match satisfactorly. If you can get a NPT to BSP adaptor supplied with your equipment then your connection problems should be sorted out. You should also consider the likely problem of how and where you are going to get any parts when the object/s you have purchased from afar require any repair work down the track.
Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians