Randy,
Welcome to the forums.
You don't need broadcasting to use Trainz. You can turn it off under settings. Note, I'm not a Steam expert and I had to query on the web and also poke around to find these settings!
In the Steam interface, click on Steam in the upper left corner.
Click on settings.
Click on Broadcasting.
You'll see a bunch of options with small arrows next to them.
Under Privacy settings, where it says friends can request or it may say something else depending upon your settings, scroll that down and choose Disable broadcasting.
There is one outstanding issue here which needs resolving. Contact the Helpdesk
Trainz Support - Powered by Kayako Help Desk Software (trainzportal.com) and request that your Steam Account to be connected to your My Trainz account. You are of course registered on Steam, but for some reason there's a glitch that sometimes prevents the Steam server from talking to the My Trainz servers where your Trainz account information is held.
The advantage of doing that allows you to download assets including routes and others such as track, building, and other trains to use with your Trainz program. Syncing the accounts will also put your Trainz version on your timeline next to your name which will help us assist you in the future. Not showing a registered account will give you limited support.