If I'm hired as a full-time truck driver is my employer able to just cut all of my hours?

The answer might depend on what state you are in but in the final analysis, you have to defend your situation yourself. If you think you are being mistreated, don't show up for work. Find another job.

Some people join unions, but it has always been known that a union costs more than it is actually worth. You really have to be your own one man union. I have quit so many jobs that it was easy to find a new job because everybody knew me. It helped that I was right, and those companies that I left went out of business.