I have often thought about making a donation to LO, but as long as it is so not user friendly I will not.
For instance it is impossible to find out how to download an English (USA) dictionary.
Can someone help?
What version of LibreOffice do you have - see Help | About for information and an icon to copy the details.
It took my about an hour to log in. I think its faster to get into Fort Knox.
But the answer is 7.4.5.1 (x64)
I believe that, if you downloaded an English version of LO that you should have an English dictionary for several versions of English. For example, my setup:
A quick web search found English Dictionary » Extensions which includes five English variants including en_US.
And of course there is the link at the bottom of the dialog box in the image above.