way to get people to help you to cover all the bits and pieces
I'm American and I'm pretty old. I have never heard about showers being to get things for the wedding.
Wedding showers often have a theme, however. Kitchen showers, recipe showers (with the gift being the utensil to cook the recipe in), bar showers (wine, liquor, and accoutrements, etc.)
Nowadays wedding showers are often for both sexes, especially if it's something like a bar shower.
Showers are not the same thing in the US as a hen party. Hen parties in the US are called bachelorette parties. Showers are usually somewhat formal and staid, bachelorette parties not so much.
Also traditionally wedding showers are hosted by the bride's friends, not family members. Remember in the movie Bridesmaids how they were fighting over who was going to give the shower?
There are often quite a few parties leading up to a wedding in the US. In addition to the shower (and there may be more than one) and the bachelorette, there is often an engagement party, and sometimes things like barbecues or dinner parties given by friends leading up to the wedding. Then there is the rehearsal dinner, usually the night before the wedding.
But we don't do the dual reception after the wedding as is common in the UK, with the A listers invited to the wedding breakfast and then the B listers invited for the evening do. There is one reception after the wedding that everyone who is invited to the wedding attends.