>>> How easy is it to get hold of a gun in the US? Do you need a licence?
The laws vary state by state. For example, only a few states ban ownership of assault weapons:
https://ichef.bbci.co.uk/news/976/cpsprodpb/E7EC/production/_124227395_us_gun_culture_map_v2_640-2x-nc.png
(If you want to read the full article that that graphic is taken from, see here:
https://www.bbc.co.uk/news/world-us-canada-41488081 )
In California, for example, Congress passed a law in 2019 denying access to semi-automatic weapons to anyone under 21 years of age. However that has recently been ruled unconstitutional, meaning that they're now available again to anyone aged 18 or over, even though it's illegal to buy cigarettes or alcohol if you're under 21:
https://www.bbc.co.uk/news/world-us-canada-61417496
It has been estimated that their are about 390 million guns in public ownership in the USA. (See my 'full article' link above). That's in country with a population with about 258 million adults.